Failed service

What a shocking service from VW Brita, took the car there for service 21/01/20 everything was done and service booked for 22/01/20 then jst when I was about to leave was told that my car cannot be serviced by VW because I was in an accident and did not fix the car at VW where I have a service plan and warranty for five years.What nonsense is all this about,? I would like to know frm VW what then happens to the warranty and the service plan still have with them. Not impressed at all and the reasons they giving me are baseless. Please provide me with a written proof starting that I cannot service my car there and what happens to the service plan and warranty i still have with VW