Sing a romantic song (at least a couple lines of it) on your partners voicemail. If you can’t sing, who cares! It doesn’t matter, they’ll still smile. If you can’t work up the courage to do it, or if auditory issues are at play, ask a friend who can sing to help you, BUT YOU STILL HAVE TO BE A PART OF THE MESSAGE LEFT! End it by saying this message has been brought to you by someone who cares about you an awful lot. They’ll save that message forever!
If you need to, tell them you’re going to call and leave a message, so they don’t pick up. It will peak their curiosity and still be a surprise.
Can’t think of a song? You can always use the age-old classic YOU ARE MY SUNSHINE. They’ll love it!