If you call me and get my voicemail, leave a message. No exceptions; violators' numbers may be summarily blocked.
If you call me and your number won't display on my caller ID, you will get my voicemail, because I never answer calls from undisplayed numbers. What should you do? See above.
If you can't call me without blocking caller ID, or if leaving a voicemail is against your religion, then don't call me.