Repairs to my phone (Acer Z5)

On the 29/11/2014 i purchased an Acer Z5 phone from Markham store in Pietermaritzburg,at About two months ago i took it back for repairs because the camera hasn't been working since January 2015 but i didn't have a problem anyway coz the picture quality is not up to standard,additional to that, THE PHONE WOULD SWITCH OFF EVERY 10 MINUTES. the gentleman assisting said Acer would take nothing less that 4 weeks to have my phone repaired. i waited 6 weeks.two weeks back my phone returned with a damaged sim slot, a second booking was made for my phone to be repaired and Markham promised me that my phone would be fixed within a week. i have to constantly nag Markham to keep me updated. today 19/02/2016 my phone returned from repairs AND THE SIM SLOT IS STILL NOT FIXED. the only answer im getting from Markham is that WE DONT KNOW WHATS WRONG BUT WE'LL TAKE IT BACK FOR REPAIRS. IVE BEEN REALLY REALLY PATIENT BUT THIS IS SOME LEVEL OF INCOMPETENCE. TWO HOURS AGO I CALL A LADY BY THE NAME OF LYNETTE(ACER),SHE TELLS ME TO HOLD FOR ALMOST 20 MINUTES THEN DROPS THE PHONE ON ME.MARKHAM HAS BEEN VERY UNPROFESSIONAL,INEFFECTIVE AND SUBSTANDARD IN HANDLING THIS MATTER. I REQUEST YOU INTERVENTION.