It's not an issue for me, but the best thing is probably to leave a sensible voicemail message, asking them to text you or call back another time?
When I pick up, I usually ascertain first when they want to make a booking, as most of the time it will be too short notice. If not, I ask a little about them, what they're looking for, and then explain about confirming nearer the time etc. I'm happy to swap a couple of texts, but it's easier to chat usually, and I always insist on a call for screening purposes anyway.