direct debit issue

i cancel my virgin broadband account 30 days before the next payment on 10th september and was told no more payments were due,they hav taken a payment out on 10th october and they said it was a mistake on there part and refunded the monthly payment but refuse to do anything about the bank charges i have recieved.
they messed two of my monthly direct debits up and i got 2 30.00 charges : (
terrible people