I used to text a former T in distress on a regular basis between sessions. We set up boundaries with it, but she never charged me. Even when she preferred to call in response to a text, I was never charged.

[edit] Oh, I meant to mention that I never text my current T, I don't think she has a work cell so it's just the main office number. I do email her between sessions more often than not, but she's never charged for it. She even said I could email as much as I want.