Went there because my car was making an odd sound ...

Went there because my car was making an odd sound from the rear passenger window. Asked representative for a diagnostic on that and the engine light that came on a couple of days earlier. They charged me a diagnostic fee and come back with a small list of repairs needed, and nothing about the check engine light. Representative tells me the diagnostic for check engine light is extra. Ok fine, so I tell him what to repair off the list they gave me. The mechanic "repaired" something else off the list and not the item I wanted repaired. Representative tells me he will give me a $100 dollars of the repair I wanted and requsted. I was mad, as the repair he made was more costly and something I could have done on my own for less than a 1/3 of the cost of the price for the repair. Would not recommend to anyone.