Number porting
Port Your Number to ONSIM
Keep the number your customers already know and bring it to ONSIM - landline or mobile. Landline ports typically complete in 10-14 working days, your existing line keeps working until the switch. Porting into Landline SIM is included; porting into the Virtual Landline service is a one-off £20 + VAT.
What is number porting?
Porting is the regulated process of transferring an existing phone number from one provider to another. Your number stays exactly the same for everyone who dials it - what changes is the network behind it and what you can do with it.
Port a landline number to ONSIM and it stops being tied to a wall socket: calls can forward to your mobile, ring natively on a Landline SIM, or feed an analogue handset through our Landline Replacement box. UK providers cannot refuse to release your number under Ofcom rules.
What can I port in?
- Landline numbers (01 and 02): geographic numbers from BT, Virgin, Sky, TalkTalk and any other UK provider.
- National numbers (03): 0300 and 0330 numbers move in the same way as geographic landlines.
- Mobile numbers (07): ported with a PAC code from your current provider, usually completing the next working day.
Setting up new rather than porting? Browse local numbers across 650+ UK dial codes instead.
The porting process and timeline
For landline numbers, the process is paperwork-light and we handle the carrier side for you. The full step-by-step lives in our landline porting guide (mobile numbers have their own mobile porting guide).
1. Open your ONSIM account
Sign up for the product you want your number on. You will get a temporary number immediately, so your service is live while the port progresses.
2. Send two documents
Email us a signed porting form (how to complete it) plus your latest bill from your current provider. Accurate details are what make ports succeed first time.
3. We run the port
We submit the transfer to the underlying carrier and track it through. Landline ports typically complete in 10-14 working days from receiving your documents, though your current provider can affect the timing.
4. The switch happens
On completion day your number goes live on ONSIM and calls start arriving on your mobile, SIM or Landline Replacement box. Then, and only then, cancel the old service.
What happens to service during the port?
- Your old line keeps working. Nothing changes for callers until the day the port completes. Keep the old service active throughout - cancelling early can lose the number permanently.
- You get a temporary ONSIM number. On SIM plans we can set your outgoing caller ID to your porting number straight away, and you can ask your old provider to forward calls to the temporary number if you want everything on your mobile early.
- Broadband on the same line needs care. If your internet runs over the line you are porting, ask your provider to renumber the broadband first - see our broadband warning guide.
Fair fees, both directions
Porting in: included on Landline SIM; a one-off £20 + VAT on the Virtual Landline service. You are only responsible for anything your old provider charges, and for resubmission costs if a port fails due to incorrect details.
Porting out: if you ever leave, moving your number to another provider costs £20 + VAT. We publish that here because a number you cannot take with you is not really your number - and under Ofcom rules no provider, including us, can block a port.
Where your ported number can live
Virtual Landline
£5/mo + VAT
Your ported landline number forwards calls to your existing mobile. The simplest and cheapest way to keep a number alive after leaving a fixed line.
See Virtual LandlineLandline SIM
£10/user/mo + VAT
Your ported number on a SIM/eSIM in your existing phone. Calls in and out use the landline number, natively, with no app. Hunt groups and deskphone pairing available.
See Landline SIMRecording & Landline Replacement
Port an 07 mobile number into our call and SMS recording plans for regulated teams, or keep an analogue handset working via Landline Replacement, with number porting included.
See Landline ReplacementNumber porting FAQs
Common questions about transferring a number to ONSIM.
Bring your number to ONSIM
Keep the number, lose the line. Open your account, send two documents and we will handle the rest.