Can I send appointment reminder texts before my 10DLC texting registration is approved?

Yes. Meeting notifications are built into the calendar system. Open your calendar (the bookable) and scroll near the bottom to Notifications. There you can customize the SMS and email sent for a reminder, a cancellation and a reschedule, and set reminders to go out 24 hours before, one hour before or at another interval.

This works for meetings and phone calls scheduled through the CRM even before your separate 10DLC texting registration is finished.