I've received multiple calls from an 'Unknown' caller ID on my cell phone saying there is an outstanding balance for a Verizon Wireless account that I had closed last June. At one point, it was said that the payment had to be made by March 20th or 22nd (can't remember exactly) before it reached the 60-day late mark... and just recently, I was told a payment needed to be in by the 13th of this month before it hit the 120-day late mark. Thing is... I've called Verizon Wireless before to check if there were any accounts still requiring payment that were linked to my name, and they said no, everything had been paid for and taken care of. The last time I heard from the 'Unknown' callers, they said it had to do with the account number alone, and wouldn't be searchable by my name.
Also, the 'Unknown' caller claims that it will affect my credit... yet nothing of this sort comes up on any of my credit reports, no account name, no payment tracking.. nothing.

Could this be a scam?