You are being called by a collection agency who has been sold Account Information of people who have past due balances. The reason why you think it is a scam is because, you are right, you do not owe them BUT an immediate relative YOU know does.
How do I know this. I have past due balance with Verizon from 7 years ago. The collection agency goes out on the internet to search your name and in that search turns up website that list people associated with you such as you mom dad etc.
Now that I said that I bet you unfortunately know that friggin deadbeat in your family who is to blame. Do what my Mom did and give that loved one a big F U for the harrasing phone calls and to pay their friggin bills.