Vodashop Mabopane, Vodacom Hisense U40

I bought a Hisense U40 from Vodashop Mabopane Central City, few months down the line it went off, wiped all my info. Took it back to Vodashop, they switched it on and said it was fine. Now it went off completely, they took it to be checked, the results are that they found liquid inside. So, the phone never fell into the water, i told them... Then they said they won't fix it under warranty because of the liquid they found. They said i must pay R1135.00 for the phone to be fixed. I then called the Vodashop Manager to complain, he said there's nothing he can do. I'm stuck with a phone I bought R999.00 which is still under warranty and they don't want to fix it because they found liquid i know nothing about.