Lack of service and invoicing issues

It all started on 12 October when I took my new Samsung, which has a cracked screen, to be fixed at the Samsung shop in Rivonia. After 2 days spent running between Rivonia and Germiston and over R400 spent on phone calls to MTN the issue was still not resolved. MTN had not put the IMEI number on the invoice and Samsung needs to have that before they can fix the phone. It is now over a month late and MTN STILL has not sent the letter to Samsung reflecting the number. I have called and emailed Devashen a number of times but have had no response. Melanie at Samsung has been wonderful in trying to help but she also has had no luck with Devashen. I am beyond annoyed in trying to get this matter resolved and MTN has been useless. I am very disappointed after being with MTN for over 15 years.