MTN Not repairing cell phone under wrranty

The LG G4 cell phone was handed in to MTN Somerset Mall on the 31st January 2016 as the cell phone would not charge, it is 7 months old and under warranty. we were promised a maximum 10 day period before it would be returned, it is now 25 days. I have contacted the branch and they cannot give me an answer when the phone would be repaired as it was sent from Cape Town to to head office and they cannot say when it will be repaired. The gave me the e-mail of the supervisor at Somerset Mall (Zahida) who did not reply to my e-mail. I was given the number of MTN head office,workshop the phone just rings after holding for 15 minutes no answer. I am paying contract fees on this phone and have no phone, not acceptable from a multinational company!!!