I would try talking with them about it but if they're hard headed, then you should definitely call animal control. Poor doggie not having anyone to play with him. ;(
I say contact a local animal rescue for tips. Especially if it's not like full out abuse but if the treatment of the dog is making you uncomfortable. Cuz it does sound a bit like neglect. You can't just string a dog outside on their own when you don't feel like playing or dealing with him/her. And now it's disrupting you and your own pets.
The rescue people may have a better idea on what to do, or at least direct you with people who are better equipped to help you out.
I know! It's really sad.