wont repair or replace phone

ive been with cell c for about 10 years now and have been a loyal customer and have never had any problems before but this is just not right I recently got a upgrade to a sony xperia z1 compact WATER PROOF!!!! phone ive been using it for about 5 months now then one day all of a sudden the phone screen just gos black but when someone calls me I could still answer it and the phone could still charge and the speakers worked so I booked it into cell c only to get the phone back a month later saying there is water damage and is refusing to repair the phone which is ridicules so I found cell c to find out whats happening the lady told me that it could of happened when I was breathing on the phone the steam from my mouth can you belive it .she said she would follow it up im still waiting for them to get back to me I now have a phone which I pay R350 a month for which I can not use at all im very upset about this and I read up on the internet about people complaining about the same thing on there sony experia z1 compact