If the account was closed then no money will be taken. If you have auto top up and the money is being taken out then the account must not be closed. Closing prepaid accounts are only done by porting the number out or by letting the money run out which isn't possible if you have autopay enabled.
Try reseting your password and see if your able to log into your prepaid self serve account then. Then login and take autopay off and let the account lapse with not enough funds to continue.