Leroy "called about my car".  Left me a voicemail.  I checked his number and look what I found.

Pants on fire, I agree with you, "Manny" and "Mike" probably work for this company.  If you or anyone else really had a good experience, post some proof, for example, lets see a copy the bill of sale of your "Corvette" and a copy of your invoice buying this advertising service.  

As far as I'm concerned, there's NO WAY IN HELL I'm paying that much for an ad with no guarantee.  If you guys are THAT good, then sell my car first "for more than I would sell it for" and I'll gladly pay your fee.  

You can also post some statistics on your success rate of selling cars.  Of course, these would somehow need to be audited by a reputable firm (not by your co-worker) because no one will believe you.  

PS - when people write in their ad "Do not contact me unless you want to buy the car", that does NOT mean "Please call me and try to sell me something".  It means "Do not contact me unless you want to buy the car".