Debited following cancellation

This morming I woke up to find that my bank account had been debited regardless of the fact that I had cancelled the contract in January. I requested immediate cancellation as my business had taken a serious financial blow and made mention that I would not have sufficient funds available to pay further. I sent all relevant documentation through and heard nothing since. Since cancelling the contract I personally disconnect our wifi and telephone to prevent usage. I'm am looking for resolution to this problem as this is not acceptable. My bank account is in the negative substantially now due to this debit.