Payment method change

[Emilie]

I received a text to say I had a late payment which was unusual as I had direct debit, I've had this set up with the same bank card and phone for over a year, and I had money in my account so I knew that wasn't the issue. Because I received this text I went to check my O2 app and my payment method had changed to pay by cheque. I originally set this direct debit up in an O2 store and I was not informed this change was going to happen, or even informed that it did happen. Has this happened to anyone else and what do I do? Im only 20 so this phone contract is important for credit score and I dont want an issue that I haven't caused to have a negative affect on this. 

Thankyou in advance  

[MI5 · Accepted solution]

@Emilie 

You'll need to call customer service.
Numbers here Guide: Coronavirus Community Help and Support 
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.
8.00am is the best time to call if you can.