Sony Experia Z3

My son asked me to test my phone by taking photos under water which I did. Shortly after this my screen starts to flicker and soon after that went blank. The phone switch on and you can hear incoming calls but cannot answer as it is touch screen. I took it to MTN on Monday and was sent back home to get the earphones supp****. On arriving back with the phones MTN did not want to take the phone as they want the charger as well. I left the charger where I worked and was willing to buy a new charger if they MUST have it. They could not help me and I left MTN very frustrated. I then accidentally dropped the phone at the car and proceeded to Sony repair in Bartlett. They noticed the scratch at the back panel, and I explained how, and took the phone for assesment. The report now indicates that they will not repair under warranty, phone is 4 months old, as there are physical abuse. I indicated that I will pay for the back cover, my fault, but the original problem I feel must be covered under warranty. They merely hide behind that abuse issue and I feel that they are seeking any marks on phones to quit themselves from repairing faulty items. So frustrating to buy expensive and NO help at al