Hi, I had my handset replaced recently and no longer get 4g signal anywhere (husband is on o2 in same house and has it. I travel abroad a lot with work, and during last 3 weeks only got messages/calls when on wifi.
Did you use the spare sim in the new phone, or your old sim card?
Current Phone: Motorola Razr 5g I also have a Planet Computers Gemini
I work in IT as an Enterprise Messaging and Collaboration Tools Administrator (Office 365, Slack and much much more) and manage hardware both Mobile and Desktop / laptop, my desk is a bit like PC World
-- We are all customers and dont have access to any o2 accounts