iPhone 14 issue with simcard

[Sparky2024]

Can anyone give me some advice 

A week ago I noticed I couldn't make or receive calls and same for text messages. My data comes on and off. I have phoned up 4 times done everything they ask, had a new  SIM card and still don't work.

i know it's not the phone because other sim cards work on it.  I am just getting called failed.

Any help is much appreciated 

[twilight+princess]

Have you checked for any outages with a local mast? https://www.sky.com/help/servicestatus/your-services/mobile
Have you reset the network?
Settings>General>Transfer or Reset phone>Reset>ResetNetwork settings.