Terrible service from Volkswagen

2 weeks back i booked my car in at Barons Claremont Cape Town, My polo vivo 2016 car radio froze and stopped working. there was no display and no audio coming out but the radio could still switch on and it still could pick up Bluetooth. I booked the car in and they worked on it for the entire day. I was then contacted by Zukile the service adviser who told me that the warranty won't cover it because they saw liquid spillage on the radio, don't know how that happened because no one is allowed to eat or drink in my car, how liquid got onto the radio i do not know. I fetched the car, started the engen and the radio wouldn't switch on, it's completely dead now whereas when i took it in it was still switching on but had no display and audio coming out. I need this to please be rectified as i'm still without a radio. I was told a new radio would cost me 7000 which i think is ridiculous. If they can't fix it then replace it with a new one coz the car is still under warranty.