DEBIT ORDER AFTER CONTRACT CANCELLED

I cancelled my son's contract (in my name) in May. He started paying pay as you go on 17 June 2015. I was debited this week again.<br> <br> I called the call centre who said it was correct and I must claim from some other department - she said she would put me through but I waited ages and got no response. I really don't see why I should be paying a month later after my son has been forced to top up his balance.