MTN Billing Department and Customer Service ***********

Three months ago I downgraded from a MTN My Choice 200 to a MTN My Choice 100 . Low and behold as per my monthly statement , I'm upgraded to My MTN Choice +S which is more expensive than my original contract. Every month on the 17th I receive a SMS "Yello, you have been credited with 3 gb data, 100 minutes and 100 sms" which is what I have agreed to and should be billed for R199. I have tried many options to rectify this , from MTN Hartbee****rt Village Mall, Internet Team and 808 without any success. Who do I need to contact to solve this puzzle as they clearly do not know what they do of have no intention of assisting their customers.