Theft by MTN

I am still experiencing the most frustrating issue support process I have ever encountered. Despite confirming the terms of my contract upgrade on 15 September, I have been charged almost three times more than I should have. The support team (through Ison Experiences) has confimed, after listening to the call recording, that I am entitled to a credit but this has not been effected. For over two months I have been phoning the call centre 3 times per week, spending an average of 20 minutes on a call, and send 3 emails per week and I am still debited incorrectly every month. I have logged a case with ICASA, sent messages to MTN and Ison complaints sections to no avail. I have lost time, money and faith in this company that has effectively ****** from me.