Porting business numbers without a single dropped call

Introduction

Number porting fails for one of three reasons: bad paperwork, a carrier that drags its feet, or a team that didn't plan the cutover window carefully enough. The technology is reliable. The process around it is where drops happen. This is a vendor-agnostic walkthrough of every step, with the specific details that separate a clean port from a day of missed calls.

What porting actually is

Local Number Portability (LNP) is the regulatory right to keep your phone number when you switch carriers. The number stays the same — only the carrier routing it changes. The process involves your losing carrier (the one you're leaving), your winning carrier (where you're moving), and a clearinghouse that coordinates the handoff. On the scheduled date, at a scheduled time, the routing flips. If everything is in order, callers notice nothing.

What can go wrong: the paperwork doesn't match the losing carrier's records, the losing carrier submits an objection, the winning carrier hasn't fully provisioned the number before the cutover, or the cutover window falls during peak call volume and nobody planned a fallback.

Step 1: gather your number information exactly

The most common porting rejection is a mismatch between what you submit and what the losing carrier has on file. Before you fill out a single form, call your current carrier and request the exact billing name, service address, and account number they hold for each number you want to port. Copy the capitalisation, abbreviations, and address format character for character. 'Street' versus 'St' is enough to trigger a rejection.

• Billing name — the legal entity name, exactly as it appears on the account
• Service address — the address registered to the number, not your mailing address
• Account number — from your invoice, not from the portal URL
• PIN or passcode — many carriers require this for verification; ask if you don't know it
• The numbers themselves — confirm each number in E.164 format (+1XXXXXXXXXX)

Step 2: sign the Letter of Authorization

The Letter of Authorization (LOA) is the legal document authorising your winning carrier to initiate the port on your behalf. Your winning carrier supplies the template. Fill it out using the exact information you gathered in Step 1 — the LOA must match the losing carrier's records. If you're porting multiple numbers, list them all in the same LOA rather than submitting separate forms for each, unless the numbers are on different accounts.

Step 3: understand the Firm Order Commitment

Once the winning carrier submits your port request, the losing carrier issues a Firm Order Commitment (FOC) — a date and time window when the port will complete. Standard FOC windows for business numbers run 5–10 business days. Complex ports (high-volume accounts, toll-free numbers, numbers spanning multiple rate centres) can take longer.

The FOC date is your cutover target. Build your day-of plan around it as soon as it arrives. If the FOC date doesn't work for operational reasons, contact your winning carrier before the window — changing a FOC date after the fact is possible but adds time and increases the chance of a partial failure.

Step 4: plan the cutover window

Most carriers complete ports between 7 a.m. and 9 p.m. local time on business days. Choose a window that minimises call volume exposure. For most businesses that means mid-morning on a Tuesday, Wednesday, or Thursday — not Monday morning, not Friday afternoon, never the day before a holiday.

• Have a forwarding number ready — configure a temporary number at the winning carrier before the cutover. If the port completes and routing isn't live yet, calls forward rather than drop.
• Brief your team — everyone answering phones should know the cutover window and the fallback number. A call that rings on the old carrier for 90 seconds post-cutover isn't lost if the team knows to re-dial.
• Run a test call immediately after the window — have someone outside your network dial the ported number and confirm it rings at the winning carrier.
• Don't cancel the old line until you've confirmed calls are routing correctly — most losing carriers give a 30-day window before the number is released.

Porting toll-free numbers

Toll-free porting runs through the SMS/800 database rather than through the local carrier clearinghouse, which means different paperwork and different timelines. Expect 3–5 business days for a straightforward toll-free port. The same rule applies: the RespOrg (Responsible Organisation) information on your LOA must match exactly what's in the SMS/800 database. Your winning carrier can look this up for you before you submit.

What to do if the port is rejected

A rejection doesn't restart the clock from zero — it gives you a reason code and a correction window. Common reason codes: name mismatch (correct the LOA), account number mismatch (call the losing carrier and verify), account in pending disconnect status (you'll need to remove the disconnect order first). Fix the specific issue, resubmit, and you're back in the queue. Most first-time rejections are resolved within two business days.

Porting into letsdial

Letsdial handles the full porting process at no charge in either direction. Submit your LOA and account information through the dashboard, and the team tracks the FOC and coordinates the cutover. If you're moving from a carrier that makes porting difficult, our support team has handled most of the common rejection scenarios and can advise on the specific fix before you resubmit.