need a refund of my purchase because my device is still giving issues.

HI I have taken this device from a Apple Store and I get my camera fixed from apple store but it is not fixed properly its showing a big line of the tubelight still and after getting my camera fixed my phone is getting heat now. Please look in this matter and find a solution of please initate this to the refund or a phone replacement if phone replacement is possible.

I am facing my camera issue from day 2nd I buy this phone and from than I am continously visiting your service center to get this issue resolved.