Poor workmanship from repair technician

A Sony Z1 was sent to the Montague Gardens repair centre to repair a non-functioning touch screen & replace a cracked glass cover. The cost of R1406 was paid & the phone was returned to MTN in Stellenbosch. We collected on the 08th or 09th September. About a week later the phone was used to take a picture in a fish tank (this device is waterproof) We have done so before. The covers were closed. We have 3 waterproof Sony devices. When the phone was in the water (not even halfway) the screen filled with water. It was immediately removed and we tried to dry it. The screen had lifted from the body and whilst drying it the screen cracked because of the movement . On 26/09/2015 the phone was taken back. I drew attention to the fact that the screen was broken due to our trying to dry it. I had 4 different techs (after numerous emails) all state the same generic response that the warranty is void due to water damage and a repair cost is involved again. We never argued the fact that there was water damage. We are arguing the fact that it was due to incompetence of the repair technician in the first place. Weeks later I am still waiting for the person IN CHARGE to contact me