Unable to cancel MTN contract to pre paid

I have been trying to contact MTN about cancelling my contract as it is the end of my contract period and I would like to move to prepaid. I have sent emails, tried calling their call center with no response at all. I refuse to pay an extra month of fee's for a contract that they won't allow me to cancel as they simply do not respond. You cannot go in store either as they cannot help you? I had the exact same issue a few years ago with MTN and it is unacceptable.

Please can someone from MTN contact me immediately and send through the confirmation letter of the cancellation of this contract to pre paid.