I didn't answer it. They didn't leave message. I assume it is thieves. Unknown callers get one chance to leave a message, then I put the number on Digitone call-blocker. Works like a dream: the phone doesn't even ring. This category of call I automatically all FRAUD.
These people, the abusers, don't stop. They don't understand that we, the abused, have tools with which to fight against them, thus preventing them from emptying our bank accounts into theirs. The telephone ain't what it used to be.