my bills are also being sent to another mobile number NOT on my account

[RobM]

Notice of my bill is being sent to my wife's phone, with BT.
Logging in to My O2 shows that there is only 1 mobile number linked to my account.
The number of my phone.

How can this be stopped?

[MI5 · Accepted solution]

@RobM 

Your wifes number must have been linked to your account in the past and that is the number logged with O2.

You need to call them to change it.

All numbers are in this guide Guide: Coronavirus Community Help and Support 
Or 202 from your O2 mobile.
Advice from an O2 Guru to get through:
When you call 202, 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.