Swap Your SIM, Keep Your Number: A 20-Minute Porting Walkthrough for 2026

Switching networks is one of those jobs that sounds like a hassle and then turns out to be a twenty-minute admin task — provided you don't do it in the wrong order. Get the sequence right and your number barely notices. Get it wrong and you spend three days locked out of your banking app while a hold message plays on repeat.

There's no clever trick to it. The rules changed a few years back to make leaving easier, and in 2026 the whole thing is fairly frictionless. But there are a handful of genuine gotchas, and almost all of them are about the texts you forgot were going to your old SIM.

The 20-minute version, for the impatient

1. Check your contract end date and any early exit fees.
2. Move your two-factor authentication off SMS where you can.
3. Text 65075 to get your PAC code.
4. Order the new SIM (or eSIM) and don't cancel the old one yet.
5. Give the PAC to the new provider when they ask for it.
6. Wait for the switch, usually the next working day.
7. Swap the SIMs, reboot, and tidy up the loose ends.

Everything below is the detail behind those seven lines.

Before you buy anything: the pre-switch checklist

Contract status. If you're still in a minimum term, leaving early usually means a fee. If you're out of contract, you're free to go whenever — no notice needed. Texting 85075 gets you your contract details if you've lost track.

Network coverage. Slightly obvious, but worth thirty seconds on a coverage checker for your home, your work and the one pub where you actually get signal. Coverage in the UK still varies street by street in some places.

Your number, written down. Sounds daft. Write it down anyway, especially if you're switching from a number you've had for years and it isn't saved anywhere obvious.

A list of everything that texts you. This is the bit people skip. Banking apps, work logins, delivery notifications, HMRC, your GP surgery, that one online account with the old phone number attached. Have a mental (or actual) list before you go dark.

Step one: get your PAC code

Text PAC to 65075. You'll get an automatic reply with your nine-character switching code, valid for 30 days. It's free, it takes seconds, and you can request it as many times as you like.

A PAC keeps your number. If you genuinely want a new number, you don't need one at all.

One thing to know: getting a PAC doesn't cancel anything. It's just permission to move the number. Your old contract keeps running (and billing) until the port actually happens.

If the new provider is handling everything for you — some do — they may use a STAC instead, which you get by texting STAC to 75075. Same idea, different plumbing. Give them whichever they ask for.

Step two: don't cancel first

This is the classic mistake. Cancelling your old SIM before the port completes can, in the worst case, lose the number entirely — and at best it leaves you without service for a day while you sort it out.

The correct order is: order the new SIM, hand over the PAC, wait for the port, and then the old account is closed automatically as part of the switch. You don't need to do anything.

Step three: eSIM or plastic?

An eSIM is a digital SIM profile you download onto your phone — no tray, no tiny plastic rectangle, no waiting for the post. In 2026 most UK networks support them on most modern handsets.

eSIMs are brilliant if you're switching today and want service in ten minutes, or if you're keeping your old SIM active in the same phone while the transfer happens. The catch is that eSIMs are tied to the device. If you're the sort of person who changes phones every few months, or whose handset occasionally goes for repair, a plastic SIM is more forgiving.

If your phone only has one physical tray and one eSIM slot, a neat arrangement is: new network on the eSIM, old SIM physically in the tray until the port completes. Then remove the old one.

Step four: switch day

Ports usually complete on the next working day after everything's been submitted. You'll normally be told a date in advance.

On the day itself, expect a short period — sometimes minutes, occasionally an hour or two — where you've got no service while the number moves across. Then:

• Put the new SIM in (or activate the eSIM).
• Restart the phone. Actually restart it; don't just stare at it.
• Check you can call out, receive a call, and use mobile data.
• Send yourself a text from another phone.

If the old SIM still works after the port date, give it a couple of hours before panicking. If it still works the next morning, ring the new provider.

Step five: the 2FA problem nobody warns you about

Here's the scenario. You port on a Tuesday. On Wednesday you open your banking app and it wants to send a code to your phone. It arrives fine. Lovely.

But some services keep a phone number attached to your account from years ago, or send codes to a number you've since changed. Others send verification texts to a landline-style record that hasn't been updated. And a few — work systems, older portals, some government services — only let you change your number by texting a code to the number on file, which is now dead.

So before you switch:

• Log into your bank, building society and credit card apps and check the registered mobile number.
• Move 2FA to an authenticator app wherever it's offered. It takes five minutes and it's the single best thing you can do for porting day sanity.
• Update your number on any work systems or portals that use SMS codes.
• Sort out your two-factor for email first — because password resets for everything else go through there.

If you do get locked out, most banks will verify you another way: a branch visit, a phone call with security questions, or a code to an email address. It's fixable, just annoying.

The common pitfalls, briefly

• Expired PAC. They last 30 days. Request a fresh one rather than ringing around.
• Name mismatch. The name on the new order needs to match the name on the old account, or the port can stall.
• Porting while abroad. Possible, but more fiddly and harder to troubleshoot. Do it at home if you can.
• Business accounts. Ports on company accounts often need the account holder to authorise them. Ask first.
• Keeping the old phone. Don't factory reset and sell it until you've confirmed everything's working on the new one.
• Assuming a port means a new contract. It doesn't. A port and a plan are separate things, and a rolling 30-day plan will port just as happily as a two-year one.

The seven-day tidy-up

A week after switching, do a quick sweep: check your first bill is what you expected, update your number anywhere you haven't (delivery apps, gym, vet, that online shop), and confirm the old account is showing as closed with a zero balance.

Then forget about it for another couple of years. Which is the whole point.