Radio not working after service

Took my car in for a service to Hyundai Vredenburg. On the way I was listening to the radio and using the bluetooth facility to my cell phone. After I collected my car from Hyundai, the radio was dead. Hyundai will not take any responsibility, claiming "coincidence" that it stopped working in their workshop. Hyundai head office emailed me to say "Unfortunately we can't comment on the FACT that it worked when taken in and on collection not working." Unacceptable.