They say, "I Wouldn't Drive That Car Anywhere Else"
This is almost a threat. It's intended to scare or frighten you into leaving your car there and letting those guys have free reign over your vehicle. If they know that you'll fall for this, then they know they have a great chance to overcharge you for a bunch of stuff you didn't need. Find out from somebody else whether or not it's okay to move your car, then make your decision.