Poor service from Vodacom

On the 16th of December 2015 I took my Sony Xperia Z3 to Vodacom, due to the fact that my phone had no signal and I could not send or receive calls and messages. I went back on the 10th of February 2016, because I did not hear anything from Vodacom. Just to find out that my phone had been laying in the back for 2 months, not fixed, not touched, nothing. It took them a further month just to tell me that my phone is unrepairable, due to water damage. Thus, I lost my warrenty. The Sony Xperia Z3 is waterproof and I never took it close to water. This seemed very strange to me as the phone still worked perfectly, it only works on wifi, not the network. I took my phone to another technican, who told me that it is not water damage, but a problem with the motherboard. I took the report back to Vodacom. They refuse to give me a new phone. I upgraded in August 2015, so the phone was brand new. I have been paying R600 on my contract every month, even though it does not work. I feel this is absolutely ridiculous. They do not even want to check if there is a faulty motherboard. Vodacom's service is shocking. I will never use their services again.