MTN cannot resolve the simplest problem

I am a contract client of MTN SA. I travelled to Botswana, in May, I had roaming on (as I always do when travelling) and I only use roaming occasionally to answer important incoming calls and NEVER to make any calls. I received my monthly MTN invoice and it included R1,213 in roaming charges. Amazingly enough this was for dialling my own number in 4 calls totally 4 hours and 35 minutes in total. I have since early July being trying to deal with MTN to get the mistake corrected.

I have now dealt with many agents of MTN on the phone and by e-mail and NONE of them read or try to comprehend my message. The always apologise and either ask me to send the invoice (which is already in their reply email chain) or ask me to send proof using my passport that I was not in Botswana.

It is now nearly 2 months later and I have not get been able to get a single person to understand that I cannot dial myself using my own number and then speak to myself for more than 4 hours.

I have no idea what to do next as you cannot get through to anyone that comprehends what my message is. This is just debit order theft.