173 MTN Service Champion ohh please tell me about

I have been trying for weeks to get through pre-paid call centre on number 173, but there has been no response from that line and I have tried so many times to get a sim sworp, I just need to keep my old number and continue using MTN as my network, but I have noticed that I am not the only one who is tremendously experiencing bad customer service from MTN, I am quite disappointed, can you please help me as I don't know what to do anymore bought this new sim card yesterday and i have been trying so many times to get thru the call centre which shows no interest in answering consumer's calls, my old number is *** (it does not exist anymore) and the new number I just bought for MTN is *** and i need this numbers to be changed to ***, i can be reached on this new sim card of ***.