Dishonest / No Ethics

On 4/2/16 took mi I6 128G to Gateway Service Centre due to phone freezing with video of what happens. Informed store that I have performed a software upgrade recently. 15/2/16 received text informing phone is ready for collection. Upon collection it was noted that no faults were found and a software UG was done! That week the phone warranty expired and the same problem surfaced. 3 month extension on repairs. Sent the phone back on 22/2/16 informing store same problem with another video of it. Malcom, store manager assured me the problem would get his personal attention and gave me his mobile number. Has never rep**** to any texts or answered that number! Get a call a week later from the store saying it needs a software UG, which I did then they did and now want to do again and it will cost me money! While still under warranty? Explained situation and phone was sent back to JHB. Received a text on 9/3/16 ready for collection. Went to store where the report says no problems detected, but I have dated video documentation of a recurring problem. Left the phone at the store being promised Operations Manager would contact me first thing today, 14/3/16, it's now 19:20, no contact. Help!!!