I am very disappointed with this garage, once but ...

I am very disappointed with this garage, once but never again.
They propose to check something, but do not say that 80 euros will be charged. That was a very nasty surprise. No discussion possible. They said if you do not pay, they will keep the car under lock and key, so you basically have no more choice than to pay .. Hourly wages are no less than 90.75 euros incl VAT.