Blacklisted by MTN through their own mistake and poor service

I was contacted telephonically in April 2017 and offered a cellphone contract which included S7H hand piece for around R600 a month. After two months of paying and not receiving my phone I contacted MTN in Canal Walk. The guys told me he would cancel this contract due to the fact that I hadn't received my phone. I thought everything had been sorted out only to find out in January this year that MTN had blacklisted me. Since then it has been a uphill struggle to get MTN to even react my e-mails. All I ever hear when I phone is that MTN will immediately sort my problem out and get my name cleared