Yes, by not including a phone number or email address in the event, Apptoto will not have the necessary info to remind the client. Alternatively, you can add [SKIP] or #skip anywhere in the event, and Apptoto will automatically skip that appointment for you, even if a phone number and/or email is detected.
What if one of my clients doesn't want to receive SMS messages, or voice calls, or emails?
You can include [NOSMS], [NOCALL], [NOEMAIL] or #nosms, #nocall, #noemail in that specific appointment. Alternatively, if you’re using our Address Books integration, you can specify individual contact preferences for each person via the “Tools”>”Contacts” tab, and changing their preferences via the Edit button.