Can a debt collector do this?

My dad owes money to an appartment rental company and they keep calling him for money. He hired a lawyer and everything but apparently after 2 years the case is still going and they are still calling him; and now they threatened over phone that they will take his wife to court because she co-signed with him. However, he is the official signer and he is the decision maker and his wife does not even have a job or pay any of the bills. So can they take her to court and not him?? can they even threaten them like this?