Iphone won't turn on

I already tried to get it repaired and sent it to apple technicians, however while they had the phone in possession, they claimed that there was water damage inside the phone. Though I never put my phone anywhere near water. They wanted me to pay 350$ or they wouldn't repair the side button. I didn't want to spend 350$ because it isn't possible that there is water in the phone, so I told them to send it back, and so they did without repairing it.