Being overcharged and getting blamed for it

Last month was that Telkom moved my debit order themselves and no one knows who did it! and after long phone calls and waiting in line to speak to 3 people, they tell me that it is sorted now, but it wasn't the first time last month, it is like the 4th month! finally they get it right this month but then a NEW problem came up, my account should be R605, but it went to R977 now! and I am still paying the people they handed me over to, and they say I have an outstanding balance since last year and that why they debited that amount, which the past 5 months they have not been saying anything! Telkom is really becoming a stress every month rather than a service provider... It looks like till I have finished my contract with them, I must always expect something new from Telkom every month which is bad news and I will have to go to the bank even if I don't want to! I cant wait for the 24 months to finish- and still my WIFI is not working but I am paying for it!