Your business card, your Google Business profile, your clients' contacts — they all have one number on them. Switching carriers shouldn't mean throwing all of that away, and legally, it doesn't have to. The FCC mandated local number portability (LNP) back in 2003, which means carriers are required to release your number. The catch is that the process has a handful of landmines most people don't know about until they step on one.
What You'll Need Before You Submit a Port Request
Gathering the right paperwork upfront is the single biggest thing you can do to avoid a rejection. Carriers verify your identity against what's on file with your current provider — and even a small mismatch kills the request.
Here's what to have ready:
- Account number — Not your phone number. Log into your current carrier's portal or call them to find the actual account number.
- Account PIN or transfer PIN — AT&T, Verizon, and T-Mobile all issue a separate transfer PIN (sometimes called a number transfer PIN or NTP). It's usually 6–8 digits and is generated on demand through your carrier's app or website. It expires — typically within a week.
- Billing name — Must match exactly what's on the account, including middle initials if that's how it was entered.
- Service address — The address on your bill, not necessarily where you live now.
- Current carrier name — Seems obvious, but MVNO customers (think Mint Mobile, Straight Talk, or Visible) sometimes submit the wrong carrier because the underlying network (T-Mobile, Verizon) isn't the same as their actual service provider.
One pro tip: pull a recent bill and use it as your reference document. Every field you submit should match that bill character for character.
How the Porting Timeline Actually Works
Wireless-to-wireless ports are the fastest. Under FCC rules, a straightforward mobile port should complete within one business day — in practice, it often takes a few hours to overnight once the receiving carrier validates your information.
Landline and VoIP ports are slower. A traditional wireline number, or a number hosted on a VoIP platform like Google Voice or a RingCentral system, can take 2–10 business days. Business lines with multiple numbers on the same account can stretch even longer, especially when the losing carrier requests additional documentation.
What happens during that window
- You submit your port request to the new carrier.
- The new carrier sends a Letter of Authorization (LOA) request to your old carrier.
- Your old carrier validates the account info — this is where rejections happen.
- If approved, a "port completion" date is set and you'll get a notification.
- On that date, service on your old carrier drops and the new carrier activates your number.
Don't cancel your old account before the port completes. That's the classic mistake. Your number lives on your old account; cancel it and the number can be released back into the pool.
The Most Common Rejection Reasons
Rejections feel random, but they almost always trace back to one of a few root causes.
- PIN/passcode mismatch — This is the number one cause. If you have an account PIN (used for customer service calls) and a separate transfer PIN, make sure you're submitting the transfer PIN, not the general account one.
- Name discrepancy — "Bob Smith" vs. "Robert Smith" will get flagged. So will a missing LLC suffix on a business account.
- Number listed under a different account — Family plans, in particular, can cause this. The number might be billed under a family member's master account, not yours.
- Active service requirement not met — Some carriers require the number to be on an active, paid-up account. Unpaid balances can trigger a hold.
- Porting a Google Voice number — Google requires you to unlock the number first inside Google Voice settings (there's a fee, currently $3). Skip this step and the port will fail immediately.
If your port gets rejected, the new carrier should send a rejection code. Common ones include "account number mismatch" (code 13) and "name mismatch" (code 14). Those codes tell you exactly what to fix.
Keeping a Vanity or Premium Number Through a Carrier Switch
If you're moving a high-value number — say, a 1-800-NEW-YORK or a repeating pattern like (212) 555-1111 — the stakes are higher and the process deserves extra attention.
A concrete example: A law firm carrying (310) 444-4444 switches from AT&T to a VoIP provider for cost savings. Because it's a business landline, the port takes seven business days. The firm keeps AT&T service running until port completion, so clients never hit a dead line. On day eight, all calls route through the new system without the number changing.
For numbers you've found or purchased through a marketplace like GreatNumber, verify ahead of time whether the number is on a wireless or landline platform — that determines which porting timeline you're working with.
A few extra precautions for valuable numbers:
- Ask your new carrier to add a port freeze or number lock once the transfer completes, so no one can initiate an unauthorized port out.
- Enable two-factor authentication on any carrier account holding a premium number.
- Keep records of your account number, PIN, and authorization documents somewhere secure.
Quick Takeaways
- Get your transfer PIN from your current carrier before starting — it's different from your account security PIN.
- Match your submitted info exactly to what's on your bill; small discrepancies cause rejections.
- Wireless ports typically complete in hours; landline and VoIP ports can take up to 10 business days.
- Never cancel your old account before the port finishes — doing so can cost you the number permanently.
- Rejection codes tell you exactly what field to fix; request one from your new carrier if the port fails.
- Add a port freeze to any high-value number once it's safely transferred.
If you're in the market for a number worth protecting in the first place, browse what's available at GreatNumber — everything from local vanity patterns to toll-free numbers across area codes like 800, 888, and 877.
