Starling Buick GMC Stuart

My 2017 Sierra, white in color. I brought it in for the transmission overheating. They said the removed the pan and found nothing wrong. The service writer Tom C. gave me my white truck back with greasy hand prints on the driver front and rear door, both fenders, hood, chrome grille, both running boards, inside driver door panel, steering wheel, and shifter. Tom said "I am sorry but the car wash was closed." He had the truck finished for 4 hours after he called to tell me it was done. When I left the dealership with my greasy truck it started smoking and the burning oil came inside the cabin via the ac vents to the point I had to open the windows and got a bad headache. The truck was shuttering and at one point refused to move. All Tom could say is he was sorry. The second time I had the truck in for the same concern they said there was nothing wrong but they saw the P0634 code set and when I picked it up it was clean. The third time I was there for the same concern they claimed to flush the transmission and inspect the transmission pump. They did not pull the transmission which means they couldnt inspect the pump, soo they lied. The fluid was brown insted of pink which means they didnt flush the fluid, they lied. The truck is shuttering still. The fourth time I was there for the same concern and even wosre now they cleared the 3 codes, P0634 P0700, U0101 and told me to take it somewhere else. Yes you read that right, the dealership that sold me the NEW truck told me to go somewhere else. This truck is 3 months old and less than 6,000 miles. It was a dealer demo and sold to me with 3,000 miles. I am currently pursuing a case with GM customer service. Stay away from this cesspool of a dealership.