My phone states "not registered on network" therefore texts NOT WORKING

[Percy]

My phone has been showing "Not registered on Network" since Saturday 7/10/23. you have sent me a new sim 'wich I have put in my phone.' but when I try to register it, I can't recieve a text to enter a code to verify it's me. I have spoken to customer services twice over the weekend and they said the new sim will solve the problem; abviously it has not as you expect the text service to be active. I am dissabled and vunerable and just undegone MAJOR SURGURY. The hospitals like yourselves insit on sending texts which I cannot recieve PLEASE HELP IMMEDIATELY.

[MI5]

@Percy 

We have no way of knowing if O2 sent you an activated sim or not.

If it's not activated, you need to get back on to O2 to activate it for you.

It could also be a phone fault and nothing to do with the sim.

Is there any way you can get to an O2 store to get both phone and sim checked?

[Oxonian]

@Percy 

I am sorry to hear of your predicament. 

If you cannot get to a local O2 retail store, could you try a different SIM in your handset, maybe one from a different network ? And could you try your SIM in a different handset ? 

That will help to isolate whether we are dealing with a SIM or a handset problem. 

Please post the outcome on here !