I can't for the life of me understand why we don't yet have dual-consent calling. Your call should only go through on my phone if you have my number and I've added yours to my address book. Otherwise you should go straight to voicemail.
That's what I do. If a call comes into my phone from a number that isn't in my address book, it just gets sent straight to voicemail. My phone won't even ring.
The only reason I don't just drop the call completely is to cover situations where a someone not in my address book might be calling me for something important.