Vodacom refuses to repair my phone

I took my phone, which is still under warranty, to a Vodacom repair shop about 3 weeks ago. A day later I was informed that it had been received at the advanced repair centre and then on the following day was told that it was being assessed. 15 days later, I was told that the phone is liquid damaged, and this had been my fault and so I need to carry the costs of fixing it. When I explained that this was impossible because the phone has never been exposed to water or any other liquid, I was told that it could be sweat from my hands and I would be sent photos on that day to show the damage. The email never arrived on that day, I only received the photos after calling Vodacom 2 days later. When looking at the photos I was surprised to see how worn \my phone"looked on the inside. If it is indeed my phone"