Worst Service Ever

I have a mobile contract with Telkom, few months ago I changed jobs and had to change my bank as well as . My salary now goes to a different bank to the one i registered my contract with. I logged in online where you can communicate with them via a chat and they told me that it was sorted out.The following month they still debited in the wrong (old) account, I called the call centre and they told me it was sorted, the following month they still debited in the wrong account, I called the call centre again and they told me they cannot change it and that I have to go to the store. I went to the store and they told me it will be effective the following month. When that following month came they debited in the wrong account still, how hard can it be to just change banking details? As if that was not enough when they debited the old account there was no money and now they charging me twice because the debit order bounced, of which it was not my fault because they had told me they will debit in the new account. Instead of paying just R200 for my contract, I end up paying R450.00 and now i have to move money from the new account to old account and which there are charges as well, I end up paying almost R500.00 a month. Am even thinking of just settling my contract, i want nothing to do with telkom ever again. HOW HARD CAN IT BE TO JUST CHANGE BANKING DETAILS, IT CANNOT TAKE 5 MONTHS TO CHANGE BANKING DETAILS. The worst service ever.