I've been burned twice in the past (when I was young and foolish) when A) leaving a vehicle for an oil change for the day, and B)when a dealer took the vehicle to the back service area where I couldn't watch, and in both cases, the work was not done....but I was charged for it.
That was many years ago, and since then I've either done my own, or insisted on watching them do the work.
My current operating method is, I buy oil filters from Mazda, then go to a drive through quickie lube place, get the oil changed (I insist on name brand full synthetic out of a bottle, rather than bulk oil), and I always ask for my old filter back (I bring a ziplock bag with me for that).
I will never have an oil change done where I can't watch.
