afni collections Trying to collect a bill for AT&T which has been settled with AT&T and disputed with Experian Bloomington Illinois

I am in receiipt of a collection letter from this anfi collection agency in Bloomington, IL attempting to collect a debt for AT&T which was settled with AT&T 2 years ago and also disputed with Experian.  This debt was removed from my credit report and have not received any more from AT&T.  When I sent the ticket from UPS showing that their equipment had been returned to AT&T, nothing more has been received from them.  This is a scam, as seen on the internet as to how this collection agency attempts to collect past debts that have been settled.  This collection agency has attempted to do this with other innocent victims.  I am filing a complaint with the Federal Trade Commission about this ongoing scam.