Z3 Sony Xperia

I purchased a Z3 Sony Xperia from Vodacom in Sandton last year, one of the features of the phone is that it is water proof. It fell into water literally for 5 seconds last week Friday and thereafter was not working. I then went to Vodacom and told them about what happend and they directed me to Vodacom care, at Vodacom care they told me that my phone is a write off because of water damage and there's nothing they can do, I should take it up with Sony in Boksburg and I reside in Sandton. One of the male consultants was actually very rude saying there is no phone that is water proof in South Africa and who said that my phone is water proof, he then went on to say that I can't prove it! This was terrible service on his part. Nonetheless besides all is rudeness, my point is the phone is advertised as water proof and it should either be fixed or I get another phone. I am on contract and I refuse to continue paying for a phone that is no use anymore. Someone needs to sort it out immediately please as it is rather an inconvenience!