Best to never answer these numbers with no caller ID, or just block them if your telephone has that capability.. They are all scams of one kind or another. They use 'spoof' numbers which are  phony computer generated telephone numbers, so they could be calling from anywhere. Scam artists and collection agencies like to use this modus operandi to glean information. There should be a law against this stuff, but the telephone companies and law enforcement agencies won't do anything about it .

Got 2 calls between 7:30 - 8:00 pm PDT and there was no response but no dial tone either. Annyoing

The number called and hung up after I answered.

Classic case of predictive dialing gone wrong. Machine sets up more calls than operators for max efficiency at our expense. Should be banned!

Called me twice today, earlier today I called the number back and message ask to push # 1 to take a short survey or push # 9 to be put on the do not call back list.