Canceled contract

Absolutely appalled by MTN! I canceled my contract last month via their call center but to my surprise it wasn't canceled and they had billed and suspended my phone ,I've called the call center numerous times , one of their consults just dropped the phone in my ear ! I've asked them to pull the call as I did request for a cancelation and their manager said he would call back . It's been over a week and still no assistance and my phone is still blocked due to their disarray!