"You're asking them to do something they are not willing to do, perhaps due to your insistence of having them follow a flawed procedure which they know will produce an unsatisfactory result. "

No, they need to tell me why they can't do it. It is the responsibility of the service provider to explain what service they can provide (or not). I can't tell them why they can't do it because I don't know.

Logically, only they can tell me why they can't do it.