Parts missing inside my iPhone

I have reported a problem that my iPhone 5s is not able to scan my bills with rear camera or take picture of my bill as the picture comes out to be blurry and no text is visible in the picture, this problem is present from quite a while. I also had a comparison with my friend iPhone 5s and found out that the problem is with my iPhone as his camera was working fine and was taking clear pictures. Earlier there was no such problem that I was aware of with my iPhone

I contacted Apple chat support and followed what they have asked me to do, to check the issue with the iPhone. After all the checkups they asked me to visit Apple Service centre as they were able to identify that the issue was with hardware.

I visited Apple store. First, I had to wait for an hour to get my phone checked and second, they opened my phone without my acknowledgment. The technician found that two parts were missing inside my iPhone one screw and one more thing near the rear camera (back tape like thing). He also made me understand the missing parts with another iPhone opened. This is the first time my phone was opened. This means there is a manufacturing defect by Apple as such incident has occurred and I have default one.

First, I want to know how come this type of incident has occurred.

Second, I have spent money to buy iPhone just because of its quality and service.

Quality – I am not getting at all.

Service - Parts found missing, and I am really not happy with the service they are providing me.

I feel depressed because of this incident and I request you to that understand that if someone is paying good money for a phone that person deserve a better service and quality.

At present this phone is no use for me as I am not able to take picture; I have travelled home after long and wanted to take picture, which I am not able to.

Please help me escalate this as I am too much depressed and angry with the iPhone 5s. I hope you will pay regards to my concern and help me with it.

Hoping for a positive response from Apple.

Please contact me at the number mentioned in your records.