DSTV double debit order dilemma

Dstv had issues with their debit orders and I was billed incorrectly for 3 months in a row. I have been trying to get my money back since 28 December and every time I contact them, they tell me a different story, in a nutshell, that I created the wrong debit order myself and that the incorrect amount does not reflect on their side. I have sent my bank statements as proof but was told it wasn't proof enough and I had to sort it out with my bank. My banker at fnb cancelled the last 2 debit orders and I paid dstv the correct amount, that was confirmed via email with a dstv consultant. The bank could not cancel the 3rd debit order, as it was too old. It is not a lot of money, around R200, but it is owed to me and I can't see why I can't get it back. In correspondence this morning, dstv claimed my debit orders bounced and they were forced to do a double debit, surprisingly with the same details of my EFT after arranging the process with them. Clearly the system is broken. My service was even suspended for a day because of the "bounce" and me subsequently "owing" them money but the next day it was reinstated and my balance was in credit. I have since cancelled, but would like to wrap this up, get my money back and a letter confirming I owe them nothing. I don't want to be blacklisted due to their ineptitude. I don't know what else to do. At no stage in the month-long process did anyone I dealt with offer to investigate or help.