Welcome to the community @Casi_Nerina
Try {{Jane Doe!!phone}} should work. We call this tiddlername!!fieldname a text reference.
More an more once you learn filters we can also use a “filtered transclusion” {{{ [[Jane Doe]get[phone]] }}} in which we can test other things.
For more info sarch in the forums, but in the following I discuss using the longform of transclude How to use the transclude widget and shorthand transcludes and Putting transclusion inside a transclusion? - #7 by TW_Tones and others.