"BMW" doesn't actually work on any cars.

The dealership is a company that is independent of BMW... I only stress this issue so folks can wrap their heads around the whole "3 way" relationship... (owner, manufacturer, dealer)

Once again, it all depends on what was on the paperwork you signed when you dropped it off. In most states the mechanic must get prior approval to make repairs, period.

The 'mechanic' is the dealer or Joe Blow at the shop down the street.... When you drop off a car, you sign a work order. Read it. DO NOT BE INTIMIDATED - they are asking you to enter a legal agreement, read it. (Actually read the one now, then you'll know what it says for next time.)

If there is anything other that $0, you want to know precisely what they are doing. Many an SA will say "The warranty will cover it, but just in case I put down $100". Red Flag. You are absolutely on the hook for $100.

There is often a area on the work order where they can enter telephone authorizations for increases- date, time, initials and amount. I cross this out as mentioned above.

If when you pick up a car, the bill is more than was authorized, simply decline to pay more. If they insisted, pay with your best credit card, note at each signature and on the copy of the work order they ask you to sign, something to the effect "Disputed amount, not authorized"

Was it an aftermarket LED style bulb?