How do I let them charge from my sim

[KingAmo]

So I have a PAYG SIM with £102.5 on it, and I was able to get a pay monthly of £7. I tried to do it at the store so that the amount and the number will be changed to my pay monthly instead of getting a new one but they didn't attend to me properly because they were closing.
I have called customer service and one of them said he will do it for me. It has been 4 good days when he said everything will be in its place but I have seen no changes and no are charging me from my bank account while I have money on my PAYG.
Is there any advice you have for me ?

[MI5 · Accepted solution]

@KingAmo 

You need to transfer your PAYG number to your monthly sim and the credit on the PAYG sim will be applied as a credit on your contract.

https://www.o2.co.uk/help/device-and-sim-support/how-to-keep-your-mobile-number

[KingAmo]

@MI5 that worked. I have been able to change it. But I don't see the money on my account. It doesn't show anywhere so far and I'm kinda worried they will still continue to deduct.

[MI5]

@KingAmo 

Bill credits don't show on your overview until your bill is generated.