Who called from 2403745400

This number called me and when I answered, they hung up

Sounds to me like it's kids prank calling people. I could be wrong, though.

This number called at 8:04 this morning and did not leave a message.

They called saying they wanted to collect a debt

I am getting the same phone calls. I answered and they refuse to tell me who they are. They said they are debt collectors but what say for who. Not sure about these people.