Infinity Insurance Company Clayton Costello (agent) Sent physical mail to my home claiming I owed them $1144.69 for some imaginary loss. Birmingham, Alabama

I received a letter from Infinity Insurance today, demanding that I pay $1144.69 for "damages" on some claim.  Never heard of this company, haven't had any accidents (ever), and I was on a boat at an island on the date of the claim, so I'm certain this is fraudulent.  The letter is very threatening (and the first one I've received), stating "If you do not respond, or next action will be referral to a collection agency of attorney for further action".  

Well, consider me responding -- I'm reporting this here, I'll be filing a US Mail Fraud complaint as this came in the mail, and I'll also report it to the California Fraud Division. I left voice mail for Mr. Clayton Costello, the letter sender.  I also spoke with someone else at Infinity Insurance Company who couldn't seem to find the claim (even with the number), so they seem clueless.