I did not recognize number, therefore, I do not answer.  It rang several times.  I will block number and/or hook up to fax machine.  There is no need to answer numbers that I do not recognize.  It is like opening email that one does not recognize.  Dont answer.  It is all a scam.  Somebody should record all these numbers and call someone like date line and/or evening news and give them a full account of all these telemakers/scammer phone number and ask why the government does not put restrictions on these scammers.

called back and it says it's a telemarketer

This is a frequent caller.  The number showing on caller is likely a spoof to cover the real number they are calling from. They are usuall calling for an alleged credit card service claiming to be able to lower your credit card rates.  They do not honor do not call lists or requests to take you off their lists.  Best result is to not answer.  The complaint site for the national do not call registry is worthless.  They don't do anything.

called, it hang up when answered.

caller ID showed "phone".