Your phone could be showing No Service for a limited number of reasons.

Most likely, there's a temporary problem with the signal delivery at your location.

Check the current status of the network here: https://status.o2.co.uk/ 

There might be a fault with your phone itself and it's rare, but there could be a fault with your SIM card.

Here's what to check.....

• Does anyone else in your vicinity have the same problem?
• If you're indoors, is there any signal, outdoors? 
• Switch your phone off and on and in between, remove and reinsert your SIM.
• Try your SIM card in an unlocked phone or the phone of another plan.com user? If service is available, your handset is defective. Contact your supplier.

One other possibility is we have taken action to prevent service for some reason, though we would have taken steps to notify you first. Please check your records.