MTN's ongoing poor service

After having resolved (or so I thought) an issue with MTN where I was billed for a cancellation fee on a cellphone contract which I cancelled before delivery, I received a final demand for "an outatanding debt of R59.97" threatening all sorts of legal action, blacklisting of the device etc. This after apparently sending numerous SMS's which I did not receive. I suspect the charge is for the new number allocated on the cancelled contract and I was assured that this number had been deleted from my account, so any SMS's would not have been responded to! And why allocate a new number for an upgrade - duh!! I have had my existing number for years - why would I want a new number? I also cannot see an invoice on my a/c for the amount claimed as outstanding. I responded to Customer Care & received an email response that the issue would be attended to within 4 hours. That time has lapsed! Furthermore my bank a/c was debited with R91.10 for the cancelled contact monthly fee and this amount has not been credited, nor have I received a credit for the R60 charged by my bankers for a stop payment I made as the debit order containing the cancellation had already been processed, The stop payment was made at the request of MTN's Dinesh who at least attended to the main issue correctly. All I want is for these issues to be attended to without further delay & aggravation!