Z3 Sony Xperia not water proof

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 happened 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. This is false advertising from both Sony and Vodacom, someone needs to sort this out immediately as I can't be paying for a phone that is not in use and that is meant to be water proof but wasn't. It wasn't even in the water for long, this is rather disappointing and I am inconvenienced now and Vodacom did not take accountability for the phone they sold to me, referring me to the manufacturer. I want the phone to be fixed or a new phone with no extra charges charged to me. This is a Sony product and has been falsely advertised to consumers!<br>