My Service now gets suspended after I paid them what I was owing, what's wrong with these people though?....#So_Furious

MTN suspended my services (Calls, Data, SMS etc) after they told me to pay a reduced amount, as a result of "goodwill credit" from my previous inconvenience. After paying the exact amount i was instructed to pay manually due to failed debit orders, they still say I'm owing and they suspend my service, I sent an email yesterday after a long call with them which yielded no results.