"+ Replacing your sim
If you’re an existing customer, you may need a replacement plastic sim or eSIM for one of the following reasons:
Your current sim is faulty or damaged
Your device has been lost or stolen
You’re upgrading to a new device that takes a different size or type of sim.
There are two ways to request a replacement sim:
Ask in your local O2 store
Call Customer Services on 202 (Pay Monthly) or 4445 (Pay As You Go), free from your O2 phone."
https://www.o2.co.uk/help/phones-sims-and-devices/activating-your-sim