Sony Experia Z1 not waterproof

On 01/08/14 i used up 2000 of my talking points and paid R7000 cash to purchase the sony experia z1 for my son who was relocating to the UK. At his farewell party it was given 2 him.In dec he came to drbs 4 a holiday before taking pics in the pool we made sure all ports was closed, he took pics just below the surface he then rinsed the phone. it worked perfect 4 the next 2days then it was going off /on and was only coming on when on charge then didnt come on at all. it was sent to sony in Boksberg were we were told that water came in thru the sim port and the phone cannot be repaired or replaced. I dont accept this decision as we made sure all ports were closed before entering the water and if the ports were open why didnt the phone switch off immediatley, it worked afterwards. I belive that the phone itself was not airtight/watersecured, the phone could be a factory default in which the water entered. i hope the phone is repaired or replaced