MTN contract - terrible service

In Aug 2018 I entered into a contract with MTN called "MTN Made for Home" This contract was for 400GB of Data (180GB Daytime and 220GB Night time) at a fixed rate of R1469pm including a free modem. This is where the good story stops and the nightmare starts. For the next coming months MTN (without fail) loaded the wrong amount of data (always too little of course). This took months and many many calls and ill promises before this was fixed. Then we started on the next issue - MTN keep on taking more money than what was contractually agreed from my account for probably the best of 8 months now. I have logged call after call, escalated calls, was asked to provide my contract not once but I don't know how many times, was referred to 10 different people…….. I've had it - I want to speak to the CEO or someone that can resolve my issue - apparently this is not possible...can anyone help. I have never experienced such bad service in my entire life!