No response to my query

In May/ June of this year my monthly contractual amount was increased. As I had NEVER RECEIVED notification to this effect I went into the Walmer Park branch and logged a complaint. After a month I had heard nothing so returned to the store where I had taken out my contract(Cape Road) and complained as well as to Kim Bridgett in the accounts department. This took place on 28th July request no ***. Yesterday I went back to the Cape Road branch and AGAIN spoke to Kim Bridgett who STILL had no answer for me. She had never got back to me since July. I spoke to Christiaan Fourie in the store and he promised that someone would call me back. THIS HAS NO HAPPENED. I have been an MTN customer since 1996 and cannot believe the unprofessional way that my complaint has been handled. I demand a refund of the increased tariff, back dated to when it was implemented as I was never ever inform of the tariff increase. I have been asking since I saw the increase to show proof that I was informed.5 MONTHS LATER AND MTN HAVE STILL NOT RESOLVED THIS. My contract comes up for renewal in January 2016, why on earth should I stay with MTN they are so unprofessional and the 808 number is never answered.