Yesterday I received a call from 000 000-0000 and today I got a call from 405 000-0000. I never answer a call that the caller ID indicates a number I don't know, but does anyone know what is going on?

Most likely a bill collector, sales call or robo call.

Those three utilize caller ID manipulation the most - though any individual can distort their outgoing caller ID to either be a non-existent number or to appear as a legit number of their choosing.