The thing about complainers...is they can only complain as much as you let them. When they start in, suddenly find something else that you have to do and hang up with them. Or, if you're just too nice and have to listen to them, let them get going...then ask them what they're going to do about it. Complaining solves nothing, and leaves the listener feeling like they're the one who is supposed to do something about it. Make them own their own responsibilities and either solve their problem, or shut up. Tell them you'll happily discuss options that can solve the problem, but that if all they want to do is whine without results, they'll find a better listener with their wall than with you.