Callerid says Fremont, CA  rang twice, no message left-may have been blocked by my call blocker.

Does Not leave Message

Phone ID says "United States."  Assume it's patched through from another country.  Did not answer a call from this number.  They did not leave a message.  I do not answer calls from numbers I do not recognize and if the call is not important enough to leave a message, it's not important enough to return.  If it happens once, I assume it was a misdial.  If it happens more than once, I assume it's a scam or spam call and it is blocked.  In this case, I'm blocking since there are several reports of a scam or spam call and the caller ID was suspicious.

Continuous calls but when I  say hello they hang up. I've been having these calls for  weeks then they start calling from different numbers but always with the prefix of 513.

Caller ID said "Fremont, CA" - no message left. Don't answer calls from unknown numbers.