Bill

[Georgia4]

I have payed my bill on the app, it has taken it out of my bank however the app is still saying I need to pay.

[MI5]

@Georgia4 

It can take up to 24 hours to update esp if due over the weekend.

If in doubt, You need to contact O2.
All numbers are in this guide Guide: Coronavirus Community Help and Support 
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.
8.00am is the best time to call if you can.

[pgn]

While waiting for O2 to answer your call, @Georgia4, you can also view your payment history in "View and download bill" section online - it updates pretty quickly.
You should also have got an e-mail confirming receipt of the amount paid, if O2 have your correct e-mail associated with Your MyO2.
Good luck!