Any reason not to honour warranty

My iPhone 6 stopped working so I initially took it to the Eastgate Branch. After 45 minutes and lack of assistance, I left the store and took my phone to iFix. They checked the phone and said they would not be able to repair as it was still under warranty and advised I take it to MTN ( no mention of water damage). I then went to the Melrose branch store next door to iFix, and handed my phone in. Now 2 weeks later, I FINALLY get feedback advising me that I must pay R6230 to repair my phone, when I called to enquire as to why this is not covered under warranty, I was advised it is due to \water damage". My phone has NEVER been ANYWHERE near water"