American RPA criminal and civil lawsuits?

So the above specified company has been calling my house, claiming that they want us to sign for papers involving a case in which my mom's mother in law from over 20 years ago owes money. I don't know to who, and I honestly don't know many details about the situation at all, but all I know is that this company, American RPA, seems to be insistent on dragging us into this case. My mother has been on the phone with them 3 times, and has been hung up on each time, one time right after she told them her name, and another right after she asked what state they operate out of (I'm not sure what the third time was for). Clearly this struck us as very sketchy, and we are doubting the credibility of this so called lawsuit company. If anyone knows anything at all about these guys, please let me know, it would be greatly appreciated.