Difficulty in cancelling an MTN contract.

It has been one month since I e-mailed the retentions department at MTN to cancel a contract on behalf of another person. I have e-mailed the request on a weekly basis for 4 weeks now. Attached to the request was the relevant information such as ID documents, and a court appointed letter giving me permission to act on behalf of this person (power of attorney). I have tried numerous times to get through centre, but no one seems to answer any calls. To hold on for 45 minutes to an hour is totally ridiculous. I have managed to speak to an operator (or champion as they are called) on one occasion three weeks ago, but she could not pick up anything on the system and informed me that an e-mail must be sent again. Why is MTN giving such terrible service especially considering that this person has been a loyal customer of MTN for almost 30 years. And what else do I need to do to get some sort of assistance with this issue?

The cell phone number in question is ***.