Are There Any Honest Mechanics?

[scruffboy]

O.K., it seems like you guys know what you are talking about and have been around, so tell me how I should handle a situation like this. I take my car in for major work (new water pump, clutch plate, clutch pump, etc) and I am given a written estimate. The work gets done in a timely fashion but they say they found something else and fixed that. Show's me the worn part and it looks legit, but adds rather large sum to bill. Shouldn't they have called me to O.K the work? What if I didn't have that kind of money on me? I told them to please call next time before doing extra work (politely) but they seem pissed. I even thanked them before for the nice job, just asked for a little professional courtesy in future. Am I wrong here?

Scruff.