Obx Auto

I have had bad luck both with the service department and the sales manager. I used to own a Buick Rainer. I took it in for a check engine light. They said it was a bad "something" (I blocked it out) and charged me $400.00. Three days later the check engine light was on again. Brought it in. They said the unit they replaced three days earlier was bad again. Charged me another $400.00. How can the part go bad within 3 days? And why didn't they stand behind their work? They said it was a design problem and the unit was placed too low and got wet. Come on! Buick designed an SUV that can't be driven in the rain? Second issue..Then I received a letter asking me to come in because they wanted to buy my Rainer. I went in and they gave me a written offer for $11,000.00. I went elsewhere and bought a car. Within a week I returned to OBX Chevy, written offer in hand, which stated "offer good for one week", and told them I wanted to sell. Then they said the Rainer had to be re-appraised by the sales manager because it may have depreciated. OK, how much can an SUV depreciate in less then a week. Answer, $1500.00. New offer was $9,500.00 and that was after I argued. Initial offer was $9,000.00.