I've heard about this company doing this. When I blocked my number, they finally answered so I could hear what they said when they answered. I just kept my phone on mute to hear if they would threaten or anything of the like.
I've read these companies will claim that you've written a check for a particular company and tell you they are going to turn you over to the authorities for check fraud unless you pay them the original amount you allegedly stole from them in the first place. REPORT TO FTC!!!