Cancellations not actioned

I cancelled 2 contracts with MTN in April 2016, for which their Retentions department sent me a email acknowledging the request. 14 Months later, I realized that I'm still paying for both of these numbers on a monthly basis. I went into a store to query this, and was told that the request was never processed. I submitted a second cancellation request in May 2017. Only after numerous phone calls, emails and visits to the MTN stores, was these two contracts cancelled. Then, I asked for a refund / credit against the 14 months I was paying for a service I did not make use of. I submitted forms, forwarded emails on 4 separate occasions, only to be told today (17 August 2017), that the credit request has still not been processed as MTN has not received any proof of cancellation from me. I have in the meantime stopped their monthly debit order, and phoned MTN customer care to inform them of this action, and that I will continue to stop payment until such time as I have received either a credit, or a refund. Today, I was threatened that if I do not pay the outstanding amount, my service will be suspended. A 30 minute conversation later with their accounts department where I was transferred between various employees (again), they still cannot give me an answer, except to say that I must make payment, or an payment arrangement otherwise my service will be suspended.