Quote:

what would you like them to ask -
"excuse me sir (must be respectful remember!), are you ripping me off by knowingly quoting on work that doesn't need to be done?"

or maybe -
"if you don't mind me asking, are you quoting on this work because the part is faulty, or because you would like to make some more money out of me by replacing parts that are working perfectly well, while pretending to do me a favour by giving me something for 'free'?"

if a mechanic/sparky finds that a car isn't charging because the belt is loose, and calls the customer tells them it isn't charging and quotes on a replacement/rebuilt alternator, that is deceptive. You are not only deliberately implying that the alternator needs to be replaced when it doesn't (why else would you be quoting to replace it?), you are also deliberately failling to mention that there is in fact nothing wrong with it, and failing to mention the actual fault you found. And in the end you have the hide to tell them you threw in the fanbelt for free like you are doing them a favour! nah, nothing dishonourable/deceptive/unethical/fraudulent there, hey mate?

Why on earth would someone in that situation ask if it needs to be done? they may as well straight up ask you if you're bending them over. Customers shouldn't have to ask if they are being ripped off.

And I have a pretty strong suspicion you would not answer truthfully if someone did challenge you on it - if you did you would be exposed as the charlatan you are, and I've never known a con man to suddenly admit to it when he is caught out.
"yeah, fair enough, there's actually nothing wrong with the alternator madam, I was just trying to make an extra few quid off you cause I thought I could take advantage of your lack of automotive knowledge and your trust in me not performing uneccesary work on your car. Besides you looked like just another usual stupid sucker that generally comes to this workshop. No hard feelings hey? Oh and BTW, try being a bit more respectful next time"

I think you have some mental issues phunk. seriously, this whole inferiority complex about smug people walking in thinking they're better than you. Well, i guess you show them, don't you... get some therapy mate