These people are trying to obtain information.
It is a way to steal identities.
I blow a very loud wistle into the speaker..repeatedly..i call the number back..eventually they answer...i blow it again!  And again.
I also call  the numbers back MANY TIMES...i put the call on hold after they answer..and call again.   I yelled into the phone...for every time they call..i will call them 50 times  and i do!
So far...the calls hv stopped.
Advice....dont let your curiosity get the best of your common sense....