MTN Voice Mail has not worked for over 7 months

Mtn upgraded their system a number of months ago, and since then, my voice mail stopped working for the past 7 months. I’ve patiently been on numerous calls with their customer service, and with a hoard of reference numbers , and after the few times where they have bothered to actually respond to those reference numbers they simply cannot do the simple task of getting the voice mail working. I tried mtn customer service again , and this time they said to call their non toll free number mtn direct, whom I called immediately. However they simply told me that their system is down , and please call tomorrow. I have been very patient, and as a doctor that needs voice mail to work, in order for my patients to leave a message , this is highly unacceptable. Seeing as mtn are required to provide the simple service of voicemail , but clearly cannot , I am forced to terminate my contract as this is considered a breech of contract due to inability to offer the required service.