Need some advice about harassing phone calls from a loan place.

My 22yo son and his girlfriend apparently took out a small loan - not sure if it was a payday loan place as the company doesn't identify themselves as giving "payday loans."  They are called Security Finance and according to their website, they are licensed to offer "traditional installment loans." Long story short, my son and his girlfriend took out a $500 loan with this people.  They had to list something like five references on their loan app.  Of course, they did not pay the loan back and the loan place has since been calling me as I am listed as one of the references.  I have spoken to these people and told them that my son does not live with me, that I have passed on their messages, and that is the best I can do.  They have his cell phone number, etc.  So they need to please quit calling me.  They still continued to call.  So I simply stopped answering.  I'm fine with ignoring their calls.  Then my sister calls me as she has a small loan with this place.  She had gone into make a payment on her loan and they asked her if she knew my son because they "noticed" that I was listed as a reference on his loan app and her loan app.  She told them it was her nephew and that she would give him the message.  Well that irritated me a little bit.  Then two days ago my 14yo daughter tells me today she's been getting these local calls that she doesn't answer because she's in school, but they leave messages saying "This is Ashley, please call..."  They don't say who they are.  So I looked the number and it is this loan place calling my 14yo daughter to try and track my son down!  Now I'm very angry.  I called my son and asked him if he put his sister down as a reference and he said he couldn't remember.  I yelled at him and told him to call these people, but he says he can't pay the loan, so why even call.  So I called these people and told them in no uncertain terms that were NOT to call me or my daughter again to which I was told that they were not harassing me, just trying to get a hold of my son.  I told them my daughter was a child and they just laughed and hung up.

 So my question is who do I contact about them harassing me and my daughter?  What are my rights?  I didn't even borrow that darn money.  I'm just a flippin' reference for crying out loud and my daughter is a minor so she legally cannot be anyone's reference!  If my son were sitting right here, I would throttle him!