Cell C, Sony Xperia Z3

I have been a loyal customer of Cell C for nearly 15 years. At the beginning of March I upgraded my phone through the Cell C upgrades division. The phone I ordered is the Sony Experia Z3. After ten days of usage the screen suddenly stopped working. I therefore sent it back to be assessed by cell c to determine what the problem was. I have just received the phone back with a note saying that it is beyond economic repair. The note stated \ber...visible corrosion"with no further explanation provided. I phoned the repairs center and they told me that the phone had water damage. This I will not accept. The phone has not been submerged in any water in the ten days I have had the phone. In any case"