Cellular phone problems, no solution from vodacom

Hi, i have sent my device in for repairs not so long ago for repairs at the Vodacom epair center in Polokwane Limpopo, and my device was returned un-repaired even though the warranty is still active, and i only have a week left on the warranty now. My device Sony Experia Z3 was sent in for repaired previously when the contract was held by Altech Autopage, and it was repaired without any issues, in fact they told me they replaced the device wit another one and gave me proof of the replacement. In April this year when my device went in for repairs after giving problems, vodcom said that the device is beyond economical repair but refuses to replace the device. They claim that the water indicator is active in the device even though the Experia Z3 has one of the highest water resistance ratings. So i asked them for proof that the device was exposed and damaged by water exposure as they claim, because i cannot just take their word that it is in fact damaged by water. I have requested this about a 14 days ago and still dont have any reply from them. my devices warranty is about to expire and I think this is very unfair of them as this is a water resistant phone. Kind regards Ebrahim Subban