An Abusive relationship with Service Provider Telkom

An abusive relationship I have with telkom. From day 1 I asked them to debit on the last day of the month they debit on the 25 and want me to be liable for the amount charged on bounced debit orders, I requested them to remove the debit order clearly because they cannot follow the signed agreement they than did last day of the month even included last charges of the bounced debit order. They took 631.70 I requested refund since I made payment myself I am told it is not possible. Telkom please refund my 631.70 and your call centre people have no respect for us as customers.