One Plus - No replacement for a faulty one plus 7 pro mobile

I have been using one plus phones for the last * years and was very happy with them until I bought the one plus * pro nebula blue *gb *** Gb version. I wanted to buy the ** GB version but was not available. Once I started using people complained
*. Noise and voice distortion.
*. Two times the mobile got switched off just like that with the screen flickering.
*. While dragging the screen to read the pages seem to be flickering.
*. While watching the video and taking an incoming call the voice was overlapping.
The first time I took the phone to one plus service station in Banjara Hills Hyderabad the guy just updated the OS and sent me back. The noise distortion was unbearable and the second time before * days when I approached them they acknowledged that the noise distortion was a manufacturing defect due to loose screws on the microphone. The complaint is seen in many handsets. The software issues they could not identify. I insisted that they need to replace the mobile and opening the back cover may have adverse effects on waterproofing. Anyways it's not a factory fix plus they are not identifying the software issues. Disappointed with the #one plus service and I am planning to raise the complaint on consumer forum.