invalid imsi

[Peter12]

I have a message on my phone    Invalid IMSI   . What does this mean and how do I disable this?

regards Peter

[MI5]

@Peter12 

Could be a dodgy sim.

Try another if you can.

[MI5]

@Peter12 

If you need a new sim, you can pop into any O2 store or call customer service.

Numbers here Guide: Coronavirus Community Help and Support 
Or advice from an O2 Guru regarding a way to get through:
If you call, when it comes to the reason you are calling stay silent for 15 seconds and you will be taken to the keypad options.
Press 2 for Everything Else
Press 5 for More Options
Press 7 for Anything Else which will put you though to someone.
Say "Upgrade", "Lost/Stolen" or "Fraud" if you have to, to get put through to someone.