Who called from 3123243634

Got a call from a law firm asking if I knew someone from 10 years ago.  Didn't recognize the name so I said no.  Who are these people.?

Got a call looking for my sister-in-law  who lives several towns away and has a different last name than me or my wife not clear who they are.

Got a bizarre message from them claiming to be debt collectors, and to call back at 888-335-6729.

number keeps calling and never leaves a message. caller ID just says 'out of area'

number keeps calling me and then says nothing when I answer