I wouldn't keep them on the line. they are not going to waste MY time which is way more important that whomever this scam person is. besides I heard if you keep a scam person on the phone, the more chances they can get control of your privacy. trust me, don't answer; report on the do not call list. if they keep calling they will be charged a fee and you could also receive money if they keep calling you but you have to put the number on a do not call list first.
I got a call on my cell phone at 4:55 PM and another at 6:54PM. Of course the dirtbags that call don't leave a name. I won't call back and let the pieces of s*** know it is a valid number.