I don't answer numbers I don't recognize anymore. I dialed back using *67 to hide my caller ID. A recording said "this number is not in service". This is just another scammer using a spoofed number.
When you answer the phone and the caller doesn't speak, that's a robo dialer looking for numbers that are answered by a live person. Your number/name goes on a list and is then given to a telemarketer as a 'live number'. They will never remove you from their lists. They are often calling from other countries and could care less about our DNC list. The gov't can't catch anyone calling from other countries and using a spoofed number.
It's best not to answer numbers you don't recognize. The more you answer the more you will be called.