Pathetic Service

I've been trying to change my debit order from 25th without success. As a result I've been paying using a link they send to me at the end of every month. The link sent to me had the wrong amount and I ended up paying 575 and not 625. I phoned them to make them aware of that and asked for another link to pay the outstanding 50 rands, twice they send the link with the wrong amount again. They said they can see the 575 but it was not allocated properly and I must wait for the billing dept on Monday to resolve, but went on to suspend services. I was off for a few days, which led to a credit of 50 and a resolution by the billing department. Now, two weeks later they claim they can't track the 575 that they admitted they received and are threatening to suspend my internet services.