i cant remember off hand, but if there is a power button hold it down.
now that i think of it, try holding the source button in.
also, when you have the screen opened, i know ther is a way to turn off the radio, but i dont think that turns off the entire unit.
it sounds like the shop that installed it, it sounds like you had a shop install it, hooked up the power source to a wire that always has power, even when the car is off. That wire needs to be connected to a power wire that has constant power only when the car is on.
Tom