I can email my regular T about stuff, and I can leave a voicemail (or email) to request a phone call from her. I do know her cell phone number (usually she uses a different work landline number) but I wouldn't text her except in some kind of extremely exceptional/awful circumstance.

My EMDR T prefers email. She has texted me once or twice for scheduling type things, but I found that kind of intrusive since we hadn't discussed it in advance. I would not text her either unless maybe I was, like, stuck in the elevator in her building on my way to my appointment or something.