They may have just put freon in it, tho. If it is leaking slowly, it may be cheaper to put one or two cans in it every year than pay a fortune to have it fixed....
I agree with Steve. When I got my 04 Denali the air wasn't that cold. Freon was down but they couldn't find the leak?
So I topped it up & all was fine until a year later & it wasn't cold enuf again. Added a can of the Leak Sealer with a can of Freon & it's been good for 5 years now. I figure the leak was somewhere in the roof since the 2nd lines go to all the back seat vents & that would have been a major PITA or lot's of $$ to pay a shop!