Fluid for Jeep Transfer Case

The dealer is getting a couple other Jeep parts for our mechanic to do repairs so I think there isn’t a problem with billing. My DH called to order the fluid and the Jeep dealer refused to order it for him, too. Believe me, we definately pay our bills on time. The dealer says we need to come in to their shop to have the work done. I can’t see why we need to do that, except so they can charge us more.