Waterproof phone returned because of water damage

I got the Sony Experia Z1 compact in October 2014. The phone was very well looked after, keptin a good quality flip cover and has never fallen or been knocked. In January the phone was used in water for the first time, after double and tripple checking all covers are very securely closed. The phone was no more than 30cm under water for no more than 5 seconds at a time.(claims to be waterproof up to 1,5 meters deep for up to 30 minutes) I noticed the camera's lens had moisture in it. after getting homeand having phone completely dry i opened cover for charger and saw it had moisture in. Then opened cover that was only opened once for sim card to be inserted and the water indicator there was also red. Phone won't charge anymore and after sending it it through vodacom they returned it saying it has water damage and a hairline crack! Contacted the malmost 2 weeks ago and no solution yet! Obviously the phone was a dud and i am now paying in on my contract every month for a phone i have not had for going on 2 months!! No help from Vodacom either! This is unexeptable as I paid more for a phone with spesific specs and expect it to live up to that or be replaced!