Well, no, actually. Customers don't care who's fault it is -- as far as
they're concerned, it's broken. ... my point is that customers dislike
"finger pointing" when it comes to resolving a problem. It won't wash.
I sympathise; customers might tend to see it as an attempt to palm the problem
off on someone else, ignore them, etc, etc. Unfortunately, it is also true
that if the problem is caused by someone else, you can't fix it yourself. I
see this all not so much as a technical problem, as rather a customer relation
All I can suggest (and I'm sure you already know this) is trying to help them
(i.e. make it plain that you care about them, and their problem), while making
it plain that the problem is not entirely within your control.
You can see if there's a workaround; you can use an analogy ("It's like if you
call someone else in another country and their phone doesn't work; calling
Bell Atlantic isn't going to make it work"); you can try and explain to them
more detail of what's going on and where the problem is, so they understand
why you can't fix it unilaterally; you say something like "we'll call the
other provider for you, but we can't say if or when they will fix the
problem"; etc, etc.
Sigh, I don't envy you guys/gals out there dealing with customers...