Tell your network provider straight away if your phone is lost or stolen, so they can block it and stop anyone else using it. If you don’t tell them straight away you might have to pay for unauthorised calls. If your phone is stolen, ask your network provider for the phone’s identification number (IMEI) – you’ll need to give this to the police.
If your phone is stolen report it to your local police station by calling 101 or going in person. Your network provider will give you your phone’s identification number (IMEI), which you should pass on to the police. make a note of the crime reference number – you’ll need it to claim on insurance.
If your phone is insured or covered by your home insurance policy you will usually be able to claim for a new one.
You can register your mobile phone on Immobilise https://www.immobilise.com/ if your phone is lost or stolen but then gets found, police can use Immobilise to return it to you (Immobilise is the world’s largest FREE register of possession ownership details)
For further information please visit https://www.citizensadvice.org.uk/consumer/phone-internet-downloads-or-tv/what-to-do-if-your-mobile-phone-is-lost-or-stolen/