Samsung S20 Call Forwarding error

[Steph10]

When I attempt to forward my calls I receive a message, FAILED To READ DATA, I have reset my phone and switched the phone off and on with no result, is this a network or phone problem.

[MI5]

@Steph10 

Try turning off wifi calling to send the codes.

[Steph10]

I've completed that task before asking on here, reset the phone, turned everything off then on still the same, call divert been working perfectly well until this morning.

[MI5 · Accepted solution]

@Steph10 

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.