Paying in advance guarantees your session. For follow-up sessions, it also means that there is enough time to resolve any payment issues prior to the session start time, ensuring that your session can go ahead as scheduled.
You can however cancel your initial session and receive a full refund as long as you do so more than 48 hours before the session start time. For follow-up sessions, if you cancel with more than 48 hours notice then you will not be charged.
We have an article here which shows how to cancel your session in your Client Dashboard, or you can contact your therapist if you would like to reschedule.