My new phone is still unusable after 3rd repair

I have been having problems with my Samsung A5 from the start,The phone was recently send in for the third time on which i was told they had to replace the main pc board, this repairs again was unsuccessful.The phone still has no signal and therefore cannot be used. Again Mtn flamwood walk (Vicky and Angie) insists the phone has to be sent in, meaning another 3 weeks waiting period without a guaranteed result.Is this the standard we must accept from MTN Branches? According to them they cannot exchange the phone because there is a small tear in the box, this is unacceptable. this is a brand new phone that is not functional. I need assistance.<br> Awaiting your apt response. <br> DC.Sadler ***