If they are not charging for the parts, the chain is the wrong length for the new frame (or cannot make the swap for any other reason) and a new chain didn't run successfully over the old crankset and cogs, what is he to do? Give the OP back a bike that doesn't work or replace perhaps $150 worth of drivechain (and that maybe he doesn't have n stock) to work with the new chain they are also supplying? Say the mechanic has a chain on hand that he knows has never seen abuse, just enough miles to match the rest of the OP's drivetrain. Maybe it was on his own bike. Is he wrong to use it? (I do think he should mention it and say that he can take if off but the OP would have to pay for new rings, cogs and chain if he wants it to work. Perhaps the OP expressed his desires re: money when he brought the bike in. Not being there, this is all speculation.)

Ben