Extremely bad customer service

After numerous attempts to get my phone back after it has been sent in for repair I keep getting sent from point A to point B. My phone was still under warranty and it just switched off. Took it in and the tech told me my phone fell and he basically just didnt click the back cover on wanting it to seem like it was my fault. There was not 1 scratch on the phone. Phone was booked in and when I called my phone was lost. It was apparently not booked in but I have my receipt. According to them they updated their systems and that could be the cause. I have been in store and called numerous times and every time the manager isn't there. They will call me back. Up to date no one has called me and the manager is never there to see to my query. Where is my phone? Why haven't I received any sort of response from them?