Bad Service

I have a Top-Up contract with MTN. Every month on the 26th I get Airtime, SMS's and Data however this month the data was not loaded, I called immediately - the call centre said it will be loaded - two hours later it still was not loaded and I called again this time they tell me it will be loaded between 2 to 11 hours waiting time that same day, needless to say it was not loaded. I called the next day twice and I wanted to speak to a Manager but was not transferred and I was promised it will be loaded also that same day. I have send two (2) e-mails with no response, I cannot talk to Management and I still don't have my Data. According to my knowledge this is breach of contract and although I have upgraded beginning August 2015 and my monthly cost is more but I don't get the service that I'm paying for.