I don't like rejecting calls. I prefer they go to voice mail/transcription, so I set my main system ringtone to a few seconds of silence, and then a custom ringtone for everyone in my contact list (plus a few additional ringtones for family and close friends).

Bonus, if I happen to notice the phone screen light up with an unknown number and I know I'm waiting for a service station to call, I can always try my luck that it is actually legit.