samsung not able to repair S6 edge

My phone went in for a screen replacement. I have one free. Got the phone back and the screen flashed in the bottom of the screen and would ******* certain apps. I took it in again a 2nd time. Got it back and it still does the same. Other than the fact that is a huge inconvenience, my phone is my life and I run all my work through it. Now I have to give it in and use another phone and that is now influencing my business. The first time is fine cause it was my fault but now it is a schlep. Other than that they have one service agent and 6 sales people meaning you have to queue for service while the sales people look at you stand around and do nothing to help. I would think such a big brand would have better service. There is more services in the store than sales going through the till. Maybe they need one sales consultant and 6 service people. I want to know how samsung is going to ease my life as this will be the 3rd time for a simple screen replacement!!!!