Contract cancellation & migration to prepaid

I was informed to call MTN on 16 August 2015 to cancel my contract and migrate to prepaid, and I did. After 3 days I called again to find out that my initial request wasn't recorded. I then requested the same again and they gave me a turnaround time of 5 working days to resolve my request. Today I called again and I told nothing had happened and the frustrating part is that MTN will bill me for something that arised from their incompetence. I had initially called in June/July 2016 to give notice but I was told it's too early to put in notice. I'm very unhappy with the service that MTN is giving me and it would really take me a lot to consider MTN again in the future. I also think that it's ******** for MTN to continue billing me after the contract had expired. I will have no choice but to consider legal action against MTN if my request is not finalised in 48 hours!!!