Sony Xperia Z3 Compact - Water Damage

Having been an advocate for the waterproof range of Sony phones since they've been released, I was utterly disappointed and felt quite aggrieved when I took my phone into MTN to be repaired after it stopped working after just over a year into my new contract. Only a month later did I receive feedback (after numerous attempts to contact them) that my device had water damage and the warranty is voided. (http://hellopeter.com/mtn/reviews/why-i-wouldn-t-buy-sony-device-from-mtn-again-***). Their feedback was totally shocking as they would not even escalate the matter to SONY or enter any debate about it and said my only option is to pay R350 to get my old broken device back. This is completely unacceptable as I the paying customer am now forking out cash for a device which I no longer have because it's said to have water damage but is marketed and branded as being waterproof?? I always ensured the covers where closed, did not keep it under water for long periods of time and thoroughly dried it each time after it was submerged as the instructions suggest. The waterproof feature is the only reason I upgraded to this phone and now I'm regretting this decision terribly as I no longer have faith in the SONY branding and its promises to the customer. More than 2 months have passed and I have not had a single interaction with anyone from MTN on how this is going to be resolved which is why I'm lodging this complaint with SONY directly in the hope that this can be resolved and my faith restored in a brand which I have held in high esteem for the longest time.