MTN CLI not working

I have been an MTN customer for over 10 years. I recently upgraded my contract and for some reason all the calls I was getting were coming through as “unknown number”. I subsequently called MTN notifying them of this problem and they said that my Caller Line Identity was not activated. I was then told that it has now been activated and all I needed to do was restart my phone. It has now been 2 weeks, I have contacted MTN over 10 times, the matter has been “escalated” about 4 times now and they keep telling me to call back in 24-48 hours. Each time with the same outcome that I just need to restart my phone and it will be sorted. This is actually unacceptable as I am a medical doctor and can’t afford to miss calls and not be able to return the calls. Very poor service from MTN. They are On the verge of losing a long time customer if they do not rectify this problem