"It's okay." It is, really, and Livvie takes another drag from her clove. She is so glad it isn't raining, there really aren't words for it. "I will, in fact, work on that. Promise." Livvie would like to live a long life. Some mages manage it and she's sure, somewhere in the world, there is an Adept that has made it to thirty. "I also promise that I will never send you an invoice. I might, if I get your address, occasionally show up and drag you off outside to be social, or something like it." Which could be viewed as a sort of billing system, she guesses, but he could always say no.
Or not give her his address to begin with. Being friends means that while Livvie might already know where this phone line goes, she won't show up without permission.