Hum, you could just display the image of the phone and the person you're calling inside it, and just use regular renpy dialogue.
If you meant voice message, it is not built in, although you can technically just display an image of a voice text (like a sound wave) and use renpy to add dub voice to that line. A cheap hack, but one that doesn't require a lot of work.
Don't hesitate if you want to precise what you're looking for!
Have a nice day