Chosen Solution

Bought a brand new iphone 7 on 03/06/2017. On 29/06, during a phone conversation I was told that there was sound on the phone & that she could not hear me well. This was confirm by another person. The phone was given to the seller for verification and the latter had it checked from an accredited agent and the diagnosis was " Metal Plate and two screws missing for AS Connector’’ and warranty void. I was shocked and very wild about this because I have never opened the iphone & could hardly understand.. What could have happened? Is this a manufacturing defect????

@balgobin possible but highly unlikely. Sounds more like somebody did something with the phone that was not divulged to you. Take the phone back to where you bought it from. Something is definitely fishy here, it stinks.