The simple answer is yes. In order to preserve the safety of both our students and tutors, we do not permit direct communication outside of the platform.
If you had asked us to relay a message to a student via the on-site Chat function about cancelling or rearranging a lesson, we may be able to facilitate this, but we can make absolutely no guarantees. We highly recommend that you stick to the original lesson time, to avoid you getting a strike and your student losing their credit for the lesson.