Faulty IPhone

On the first of Feb 2015 I upgraded and took a IPhone 6. 2 weeks later it died on me, I took it to the repair center in midrand for a warranty assessment and it was approved. Because I had to fetch a new one where I bought it I only went a few weeks later. So on the 6th of March 2015 I went to MTN in westgate to get a new phone. On the same night I picked up that the speaker seems to have a problem especially when people are calling me because they cannot hear me. I thought maybe it could be the network but it persisted until the next day. I started using the headsets to answer my calls and people could hear me perfectly. So yes the problem is the phone and not the network. I have been running up and down the past month because of this phone and I am sick of it. Iphone is supplying you guys with faulty devices!!! A plan must be made because I will not remain phoneless again nor will I sit with a NEW phone that's giving me problems!!!