These are two different things and most of the bad feeling in this trade comes from a garage treating them as one.
A service is known work. Known oil, a known filter, a known list of checks and a known number of hours. So we quote a service as a price, and the invoice says the same number. If it does not, the difference is ours and not yours.
A repair is not known until the car is on the lift with the wheel off. Brakes are the plain example: until the wheel is off, nobody can tell whether you need pads, pads and discs, or a caliper that seized six months ago and has been eating one pad ever since. Anybody who gives you a firm figure for that on the telephone is guessing and hoping you will not argue at the office.
So a repair booking buys the inspection and the figure that follows it. Nothing is fitted before you agree. If the car turns out to need more than was agreed, the work stops and somebody rings you, with the figure, before carrying on.
The rule everybody here works to is the short version: the invoice never surprises anybody.