MTN customers - beware!

About a month ago I upgraded my contract and received a new Huawei Y9 cell phone. Initially everything was fine, but last Monday the cell phone suddenly could send and receive SMS's, send and receive Whats App, receive voice messages, but not dial any numbers which meant that no voice outgoing voice communication was possible. This was reported to MTN Cape Gate and MTN Customer Care by e-mail. MTN acknowledged, apologized and promised to communicate when the problem was solved. To date, nobody in Cape Town, despite the hard work of Eugene Barnes, nor Johannesburg, nor India where the problem was reported to, has been able to fix the problem. A SIM swop was done yesterday, with instructions to leave the phone off as the system would take between 2 and 24 hours to activate the card, which I did, only switching on after 24 hours. The problem still had not been solved. An enquiry to MTN Customer Care as to what is my next step is to have a completely working cell phone has, to date, not drawn any response.