How to Port a Business Number Without Missing Calls

The short answer

You can move a business number to a new provider without a stretch of missed calls if you do three things: keep the old service running until the new provider confirms the number has moved, choose the switch date yourself, and have the new setup built and tested before that date. The avoidable causes of lost calls are an account cancelled too early, a switch on a busy day, and a new system that nobody tested.

This guide covers the United States and Canada. It is educational, not legal advice, and the rules are as of October 2026. It does not promise a porting duration: the old and new carriers set the actual date, and the regulatory intervals quoted below start only once a complete, accurate request is in.

Why a number can go quiet during a port (and usually does not)

A port is not a reconnection. Your new provider sends a request to your current provider, the current provider checks it against its own records, both agree a date, and on that date the routing for your number changes from the old network to the new one. Until that moment, calls keep going to the old line exactly as before.

The rules are written around that switch. In the US, an accurate and complete Local Service Request received by the current provider between 8 a.m. and 1 p.m. local time is eligible for activation at midnight the same day for a simple port; anything later counts as received at 8 a.m. the next business day. In Canada, the CRTC approved new industry wording in July 2026 explaining that while a number is physically moved between switches, it can reside in both the old and the new provider's switches at the same time, and the old provider can use a temporary routing trigger to manage call-routing problems during that transition.

So the risk is concentrated in a short window around the switch, plus three avoidable failures:

The CRTC's own consumer page warns that you might experience a disruption in service while the number is being transferred, including disruptions to 9-1-1 services. Planning around the switch matters even when everything else is right.

Rule 1: never cancel the old service first

This is the one mistake you cannot plan around. Regulators and carriers all say the same thing:

• FCC: " Do not terminate your service with your existing company before initiating new service with another company." You contact the new company and give it your 10-digit number and any other information it needs.
• CRTC: " Most importantly, do not cancel your service before you switch to the new provider." The same page lists having already cancelled without starting a transfer as a case where you will definitely need a new phone number.
• AT&T: if you disconnect too soon, you'll have to reactivate the number before the transfer can be completed.
• T-Mobile: your account with the previous provider must remain active, and you should not cancel until the transfer has been completed.
• Verizon Business: keep the account open and the line active until the move is completed; the new carrier contacts Verizon, transfers the number and disconnects the line.

In practice, the port itself ends the old service for that number. You do not need to phone the old carrier to cancel the line you moved. What you may need to cancel afterwards is everything else on the account (see "After the port" below).

Two details that trip people up:

1. Do not regenerate the transfer PIN. Verizon says not to generate a new Number Transfer PIN once you have given one to another carrier, because it may interfere with the port-out. Verizon's PIN is valid for 7 days; AT&T's expires after 4 days, or 14 days for business accounts. Request it close to when you submit.
2. Pay attention to locks. AT&T will not transfer a number while Wireless Account Lock is on; Verizon requires Number Lock to be disabled before a PIN can be created.

Choose the switch date and time

You usually can ask for a date rather than accept the first one available. Use that.

United States. Under 47 CFR 52.35, carriers must complete a simple wireline-to-wireline or simple intermodal port within one business day, and a non-simple one within four business days, "unless a longer period is requested by the new provider or by the customer." Business days are Monday to Friday, with 8 a.m. to 5 p.m. as minimum business hours, excluding the current provider's holidays. "Intermodal" includes ports involving interconnected VoIP. The FCC describes simple ports as ones that generally do not involve more than one line or more complex adjustments to switching equipment.

Those are regulatory intervals once a clean request is in, not end-to-end timelines. Providers' own estimates are longer: Twilio, for example, says US ports typically take 5 to 15 days once all information is submitted, and can take 4 weeks or longer if the current provider rejects the request.

Canada. The CRTC set the simple intermodal interval (wireless to wireline and back) at the LEC-to-LEC interval, "currently two business days", and simple wireless-to-wireless at 2.5 business hours (Telecom Decision CRTC 2005-72, 20 December 2005). The CRTC consumer page says mobile ports can take a few hours, and landline to mobile or the reverse typically up to 2 business days.

Picking the moment (practice, not rule):

• Choose a weekday that is normally quiet for you. Avoid Mondays after a long weekend, month-end for an accounting office, or the first warm Saturday for a landscaper.
• Avoid Fridays. If anything needs fixing, you want both carriers' business support open the next day.
• Make sure the people who will test are working that day.
• Ask the new provider for the confirmed date in writing and put it in the team calendar.

Prepare the new service before the port

Everything callers will hear and every phone that will ring should exist and work before the number moves. Many providers let you build the new setup on a temporary number first; if yours does, use it.

Pre-port build checklist:

• Greeting recorded or typed, saying the business name the way customers know it.
• Menu options written and tested: each key goes to the right person or mailbox.
• Every phone that should ring has been rung once from the new service, and the person answered.
• Ring order and ring times set so that a missed answer falls through to voicemail, not to silence.
• Voicemail delivers where you expect (email inbox, app), and someone owns checking it.
• Business hours, time zone and closed-day settings are correct.
• Staff know what the new caller ID looks like when a forwarded call reaches their mobile.

If you need menu wording, a set of call flow templates helps you write the open-hours and closed-hours prompts quickly.

A forwarding bridge: when it helps and when it does not

There is no regulator guidance on forwarding during a port, so treat this section as common practice rather than a rule.

Before the switch, your number still rings the old line. If what you are really changing is who answers (for example, moving from a desk phone to staff mobiles) you can sometimes start that change early by turning on call forwarding on the old line to a temporary number on the new service. Callers then reach the new menu days before the port, and you find problems while the old line is still yours.

Cautions:

• Forwarding usually costs extra on the old line, and some features or plans do not allow it. Ask first.
• A number that is itself a remote call forwarding service (a number with no physical line that only forwards) is not a simple port: the FCC lists remote call forwarding among the complex switch translations that take a port outside the simple category. Expect the longer interval.
• Turn forwarding off or let it lapse with the port. Once the number moves, the old line's settings no longer matter, but a second, unported line on the account could still be forwarding somewhere.

Switch day checklist

On the agreed date:

1. Watch for the authorisation text (Canada, mobiles). For Canadian ports, Twilio says you must approve the port within 90 minutes of receiving the losing provider's approval text, or the port is rejected. Make sure the phone that receives that text is with someone who knows to reply.
2. Keep the old phone switched on. Until the port completes, it still carries your calls.
3. Wait for the new provider's confirmation that the number is active on its network.
4. Test from outside, in this order:

5. Repeat the tests a few hours later and again the next morning. If one network still reaches the old line, note which one and the time.

Special cases

Moving a landline number to a mobile. The FCC warns that when porting from wireline to wireless there may be a period when you have two telephones with the same number, and that wireless 911 location and callback services may be affected during the transition: calls should go through, but 911 operators may not be able to call you back if disconnected. Ask the new company before porting whether 911 will be affected, and keep a separate working phone on site during the switch.

Several numbers, or several lines on one account. A port involving more than one line, or complex features, is non-simple under the US rule and gets four business days rather than one. The FCC's description of simple ports includes "an account only for a single line" and no complex switch translations such as Centrex, ISDN, AIN services, remote call forwarding or multiple services on the loop. If you are moving one number off a multi-line account, say so up front, and ask the old provider what will happen to the lines that stay.

Toll-free numbers. A toll-free number moves by changing its Responsible Organization (Resp Org) in the Somos registry, not by an ordinary local port. A non-emergency Resp Org change can be scheduled for any date within the next 30 days, and the letter of authorisation must be dated within 30 days of that date. That makes toll-free numbers easy to time: ask your new provider to schedule the change for your chosen quiet day.

Bulk ports. Twilio quotes 4 to 6 weeks for bulk ports of more than 50 numbers. For a business with a main number plus a few direct lines, a common approach is to port the main number first, confirm it works for a week, then move the rest. Staggering costs a little time and limits the damage of any one rejection.

If calls drop anyway

If test calls fail after the confirmed time, act in this order:

1. Call the new provider first. It submitted the port and can see its status. Give it the number, the confirmed date and the exact symptom ("calls from carrier X still reach the old line", "calls get a 'not in service' recording").
2. Then call the old provider, especially if the number has gone completely dead. Ask whether the port was completed on its side and whether the number was released.
3. Write things down: time of each failed test, the network you called from, ticket numbers.

A short script for the call:

"We ported [number] to [new provider], with a confirmed date of [date]. Since [time], calls from [network] [reach the old line / get a not-in-service message / ring nowhere]. Can you confirm the port is complete in the number portability database on your side, and open a ticket for incomplete routing? Please give me the ticket number."

In the US, if a provider will not cooperate, the FCC accepts porting complaints online, by phone or by mail.

After the port: what to cancel, and when

Once the new provider confirms completion and your tests pass:

• Cancel everything else on the old account that you no longer use. T-Mobile notes that remaining lines with the previous provider may need to be cancelled to avoid unexpected charges. Verizon says that if you move your last phone line you must also cancel connected device lines such as tablets or hotspots.
• Expect a final bill. Your contract may contain early termination fees or balances you still have to pay, even though the old company cannot refuse the port because of them.
• Save old voicemails before the switch. Voicemail stays with the old service; T-Mobile, for example, says your voicemail will reset after the port completes.

Many owners keep any separate, unported service (an old fax line, a second number) for a week or so after the switch while they watch for stragglers. That is a judgment call, not a rule: there is nothing to keep for the ported number itself.

Port-day plan on one page

FAQ

Will my voicemail transfer? No. Recorded messages and greetings live with the old service. Save anything you need before the switch and record or type a new greeting on the new service.

Can I keep the number on my old plan while I test the new one? Until the port completes, yes: the old service carries the number. After completion, the number exists on only one network.

Will customers notice the switch? If the new menu is ready and the switch is on a quiet day, most callers notice only the new greeting. A short routing gap around the switch is possible, which is why the timing advice matters.

What if the port is rejected? The most common reason Twilio gives is incorrect name or address information. Ask your current provider for the name and address on its customer service record and resubmit with those exact details. For more on timing, see how long number porting takes; for the rules in both countries, see the porting guide.

If you are bringing a number to Auto Attendant, the app runs an instant portability check, has the authorization signed online, lets you request a date at least 8 days out, and charges nothing until the number has moved.

Sources

1. Porting: Keeping Your Phone Number When You Change Providers (consumer guide PDF) - FCC; do not cancel first, simple-port description, wireline-to-wireless and 911 cautions, fees, complaints; last reviewed 3/9/20; accessed 2026-10-28.
2. 47 CFR 52.35 Porting intervals - eCFR (up to date as of 10/27/2026); one and four business day intervals, 1 p.m. cutoff, intermodal definition; accessed 2026-10-28.
3. FCC 09-41, Local Number Portability Porting Interval and Validation Requirements, Report and Order (13 May 2009) - FCC; description of simple ports and complex switch translations; accessed 2026-10-28.
4. Get a PIN to transfer your wireless number - AT&T; early disconnect, PIN expiry, Wireless Account Lock; accessed 2026-10-28.
5. Transfer your phone number to T-Mobile - T-Mobile; keep the old account active, voicemail reset, cancel remaining lines; accessed 2026-10-28.
6. Port out my number - Verizon Business; keep the account open, do not regenerate the PIN, connected device lines; accessed 2026-10-28.
7. Voice guidelines: United States porting - Twilio; typical timelines, bulk ports, most common rejection reason; accessed 2026-10-28.
8. Voice guidelines: Canada porting - Twilio; 90-minute approval text; accessed 2026-10-28.
9. How do I submit a ROC HDI request as a Resp Org user via the TFNRegistry - Somos; scheduling a toll-free Resp Org change within 30 days, LOA dating; accessed 2026-10-28.
10. Switch providers and keep your number - CRTC; do not cancel first, typical times, possible disruption including 9-1-1; date modified 2022-07-06; read via Internet Archive copy; accessed 2026-10-28.
11. Telecom Decision CRTC 2005-72 (20 December 2005) - CRTC; two-business-day intermodal and 2.5-business-hour wireless intervals; read via Internet Archive copy; accessed 2026-10-28.
12. Telecom Decision CRTC 2026-185 (24 July 2026) - CRTC; switch provisioning during porting, number residing in both switches, 10-digit trigger; read via Internet Archive copy; accessed 2026-10-28.