MTN

Every month my phone gets cut off twice a month when i am only supposed to pay my bill by the 17th of every month. I go into store and pay my bill at the beginning of every month and have never missed a payment. every time i call the call center someone tells me something different. I ask to speak to a manager three times but they say they are on a call and they will call me back but have never heard a thing. I went to the bank and got all my proofs of payment over the past two years then i phoned MTN call center to send them my proof of payments but they said they don't need them as i am up to date with my payments yet they still cut my phone off twice a month. This has been going on for over 6 month. very frustrating and inconvenient that i have to leave work and none can help me instore or at their customer service