You would need a 5G sim, and to be in an area that has 5G masts @Kevster.
Did you get a new sim with the phone? If yes you should swap to that (how to guide below):
Guide: Sim Swap: a mini guide 2017 update
Once the sim is active, assuming you are in a 5G area you should see that.
Check your postcode on the this page once it loads (there will be a map of the UK):
https://www.o2.co.uk/coveragechecker
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
