Scammer

Cold call, doesn't leave a message. I DON'T KNOW YOU, AM NOT ANSWERING/RETURNING THE CALL. Scammer for sure. BLOCKED.

I answered - there was a 10 second delay and then they hung up so assuming it was spam and blocked number

I let call go to my answering machine, their system reacted to my recorded voice, then an Indian sounding voice said "hello ... hello ...", realized it was answering service and hung up without leaving a message. So obviously this number or similar is not worth answering.