Coming back to O2

[KKubisova]

Good morning, 

I had a contract with O2, which ended in September as I was moving abroad. However, I now wish to come back to O2, while keeping the same number and possibly SIM card. 

I am not able to go to the shops, as I am not currently in the UK. Is it possible to re-activate the old sim card with my number online? 

Thank you, Katerina 

[gmarkj]

Unless you told o2 to cancel then the old sim card should still work.
Have you been paying the monthly bill?
Have you tried using it in your phone?

[MI5]

@KKubisova 

Unless your contract is still running as said above, you may possibly be able to obtain the same number, but you will need a new sim card.

You need to contact O2.
All numbers are in this guide Guide: Coronavirus Community Help and Support 
Or http://www.o2.co.uk/contactus
Advice from an O2 Guru to get through:
When you call, you will be asked for 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.
You can also try saying "Upgrade" or "Fraud" to be connected to an advisor.