Mtn has a bad costumer client service

So me and my husband have 2 contracts by MTN... We pay the contracts 5 days before deduction so the payment is on time. Now my husband's sim card is marked on grey which mean his contract is off. On the app in the beginning of the month the outstanding amount shows R0 then 3 days after that it shows outstanding R160 or sometimes R300 then in the middle of the month the outstanding shows R0. My husband tried to call mtn the 135 and 086 135 doesn't even work. On facebook we don't get much help. We have proof on bank statements that we pay MTN every month the exact amount we have to pay!!! But clearly they put off your contract like they feel they want to