Failure to honour warranty for Sony Xperia Z3

I took out 2 cellphone contracts in December 2014 for the Sony Xperia Z3 which is advertised as waterproof. Both phones were put to the test, after taking all the necessary precautions stipulated by the manufacturer. One of the phones was perfect after taking photos underwater but the other one just shut down. Water could be seen having entered by the power button. I took the phone in for repairs in January 2015 and have had no joy from Telkom. They are not prepared to repair or replace the phone as it is water damaged and keep referring me to take the matter up with Sony. My contract is with Telkom and they need to honour the warranty of the products that they sell and it is their responsibility to take the matter up with Sony. The sales person, Lynette, agrees that these phones are problematic and that they have many returns and complaints but Telkom aren't interested in rectifying the problem. She even said that she now discourages customers from taking the Sony cell phone. She called me on Friday confirming that they will not repair/replace the phone and I can take legal action if I want. Her area manager refuses to respond to my many e-mails.I do not recomend Telkom at all