Bad bad service and taking own amounts of debit orders

Telkom is the worst service provider!!! We have a contract with them and one debit order bounced, so now they are debiting their own amounts like x4 imstalmemts so instead of my usual 501 payment, they are debiting 2000 as they wish, called them and they were not very helpful! We want to cNcel this debit order and make eft payments!!!!! Guys I dont recommend telkom as a provider of choice! They dnt put the customer first!!!!!