Redline Recovery Service

I keep getting calls from these people and the debt that they are calling about isn't even mine they are looking to get in contact with my Ex-Mother in law how do I get them to stop calling me since I don't have any correspondence with her anymore and I wouldn't know how to get in contact with her even if I did. My ex husband died a couple years ago so I have no contact with that family anymore. Does anyone have any suggestions? I call them back and I get told to leave my name and number I am not about to do that because I have no reason for them to be calling me for her debts or his.