Nightmare contract

I app**** for a contract upgrade on 11th on the 14th the phone arrived on the 17th I realised there is a problem with the phone I took a video with my other phone and on the 19th I went to mtn store ****wood Uitenhage they said they can't assist online customers and on 21st problem got worse I took another screenshot and 23 I went to Baywest mall they also said they couldn't help me,they suggested I must contact Facebook mtn, because calling 135 has been a nightmare.the Facebook team said I must go to mtn cape road pe,upon arriving there they first didn't want to help me but they eventually took my phone but promising me nothing when will I get the phone now It's the 2nd September I haven't received a word from mtn.when I call 135 I am transferred to different departments and my call is cut off without speaking to relevant person