Legal Action Sony Xperia Z3

Bought Sony Xperia Z3 in December. Did all that they say I must do to take it under water and take pics and short video. After the fone being sent here and there it comes back with the same result. A fone that is advertised that can go under water, the port where the Vodacom assistant opened to insert the sim card let water in damaging the device. After taking the fone myself to SSSCellular they give me the same report. Fone damaged due to water although I could have told them that. Sony SSSCellular say they cant replace fone for me... Where do I go from here??? Seeking legal help. this is a fone that costs almost R10th and this is the service one gets from Sony. Why do they advertise that the fone can go under water for so long so deep if I took the fone for less then 3 minutes under water in front of friends bragging about my new fone to be so disappointed... my friends just say.... why did you fall for that one... BAD Advertising SONY