next time they call, answer the phone, and have them verified the social, they can tell you when it was opened, it might be fraud or just a simple name confusion mistake from the original creditor, these accounts are given to collection by the original creditor, they take the info that they receive, it might be someone else, if it's fraud go to the police, if it's not on your credit it's not yours, but to make the calls stop you need to speak up, they will work with you, because to a collector time is money, they're not going to waste time dealing with someone who doesn't owe, trust me i know, good luck