Contract service off

I recently upgraded my contract with MTN and have never had any debit order issues in March this year one month after I upgraded I've been having problems with my network. a short while after that I received an sms stating that my service will be put off due to uncollected debit orders which I was never informed of. After paying the amount that I was asked to my service still was not put on. After going back and forth to branches and paying my monthly instalment cash at the Zevenwacht branch my cell phone network is still off. I've been contacting the call centre and they now claiming that I need to pay in another R300 just to put on my service. My contract is up to date and has been paid in cash every month yet they still claiming another extra R300. I've confirmed with the guy working in Zevenwacht branch that all my payments reflect yet he told me I cant make a cash payment this month as my account has now been handed over to legal. I'm still sitting with a phone that useless which is only costing me money each month. I would like to know how they call this service...cause I call this paying for nothing...not to mention all the airtime and data I've been losing out on. irritated