How did they get my number.  Rude beyond belief.  Will not call them again to get my number removed from their files.

Hey scumbags if your legit then don't block your number. I really want to know how you got my number. If you call me again I will report you to the authorities.

Don't fall for it, they are scammers.  They want you to give them money, they sound very convincing but I can tell you that legitimate bill collectors don't talk to people the way these scumbags do. They sound convincing cause they aren't the regular Nigerians that usually call and harass you.

Yes - threatening to serve notice pending a litigation suit