Caller showed up on phone as "Anonymous". Right there's my policy Do Not Answer. If it was a relative/friend in trouble, they'd leave a msg.
A lot of people get annoyed with these kinds of calls - try this - say you 'accidently' answered one of these calls, you get a human on the other end, they begin to ask a lot of questions, interrupt them by saying something like 'you have something on the stove, could they wait a second?', put your phone on 'mute' and leave them 'hanging on/waiting'. Don't worry about missing another call in the mean time - you should have 'call waiting' in your plan, so you shouldn't have to deal with them that time again. do this for any other BS caller. they annoyed you annoy them!