We have kids working in dangerous occupations...of course I answer especially if it is late at night.  Caller ID doesn't always mean it isn't important.
After 25 years I had to have our number changed.  Once you are on a list it is sold and resold to others.I complained bitterly to every official "trouble shooter" I could get a hold of.  

I finally got a sympathetic ear from one of the phone representatives because......ready for this?  She could not stop anonymous phone calls that woke her up nearly every morning around 1 to 3 am...
I am happy to say...now, only the PHONE COMPANY CALLS ME to solicit!!!
Good Luck.