unable to repair my cellphone of 3 weeks old

I purchased a Sony z3 at altech autopage and was told how to take pictures underwater as it was a waterproof phone.I clearly followed all instructions given on the day of purchase and finally took a picture only to discover that the phone wouldn't switch back on.I?It was sent to a repair centre and after a month I got a call to collect the phone at autopage store in N1 city mall and I was told that it failed the repair test and could not be fixed.I just had the phone for 3 weeks and I signed a 3 year contract.No extra customer care service was granted and they store manager could not advise me with any further assistance.The only option given was to pay in R9000 cash to have the contract cancelled.