John Lane Tax Sale Lists/Fast Cash Cancelled Subscription. Turned me over to collection when there was no amount due. Westminster, Colorado

Purchased John Lane's program with the manual and 8 cd roms to listen to regarding fast cash program?  I did not like the program and returned it with usps shipping confirmation showing delivery and receipt by Co of these unused materials.  Lane advertised for this program a 3 month 100% money back guarantee. After i sent it back,  my charge card was credited the first payment. Then within a month later, i get a letter from a Debt Collector trying to collect the 2nd payment for the program that was returned.  I wrote them a cease and desist letter, informed them there is no balance due, and their pursuit further would be a violation of the Fair Debt Collection Practices Act and a violation of Florida's Unfair Trade Practices Act, subjecting them to treble damages, consequential damages, attorney's fees and costs if they do not prevail.  Will contact the FTC and BBB as well if they proceed .  False Warranty may also violate Magnuson-Moss.  These people are imo scammers, liars and snake oil salesmen.  This is bad and fraudulent business practices.