The labor charge for the LTE upgrade is fixed, but that doesn't mean you should be paying labor twice for the same work. The labor charge to open that part of the dash, etc., should not have been billed on the other work, since it was already billed as part of the LTE upgrade work, and was only performed once.
Either way, it's a "fixed price" project. Even though the dash was out for service, they still charged $500