Hyundai *****ed me

Today I booked my car for a service at Wilropark Hyundai, Now I'm being told they cant release my car without a payment because they had other things fixed. Who did they tell about that before and no one gave me a quotation for that and where did they get a consent to say they can go ahead. The only agreement we had was for a service which would be covered by my service plan with MFC. This is ******* because no one liased with us to tell us about those things. I need this looked into and refunded. I was left with no choice but to pay because I'm the one who will be left with no car. I am disgusted with the service I got from them being my first time there.