MTN Voicemail Issue

There was an issue with the MTN voicemail for the last few months. Issue : Whoever calls my number cannot leave a voicemail. Calls have been made on a regular basis to MTN for the last few months, to resolve the matter. I was told on numerous occasions that this issue has been escalated, however no resolution. Unfortunately MTN does not communicate effectively within it's own organisation and I find that the same issue has to be explained over and over to MTN. The call today was dropped by the call centre agent and call was automatically transferred (as a new call) to another call centre agent . The MTN Supervisor did not wish to speak . Please advise