Keep on debitng my account after context cancellation

I sent my form for cancellation on the 5th of October. The agreement was that my cancellation will take 20 to 28 days for cancellation.. even today telkom mobile didn't cancel my contract and they still debit my account. When I make follow up with them what they say, they apologised without cancelling my contract. They apology is not helping because they are busy taking my money on my account.