water damage Sony Z2

Good day, I purchased a Sony Z2 from Vodacom last year August, In May this year I went on holiday, I went underwater to take a picture, and before I went in I made sure da flaps was closed because that's what the manual said, but that didn't make a difference either because when I came out of the water I saw that my phone was frozen and wasn't working, this was the first time I took my phone in the water from I time I bought it, when I took it to Vodacom for repairs they told me they can't repair because it's a water damage, how can a waterproof phone get water damaged? I'm not going to pay R500 a month for a phone that's not working, Sony or Vodacom must repair my phone or give me a new one or they must stop my contract then I can bring Sony up for false advertising because when advertising for the Sony Z2 they did not state that the flaps must be closed underwater