Cancel a session you teach right from its detail page — booked members are notified and refunded automatically.
My Schedule → open the class you need to cancel. Upcoming sessions you teach show a "Cancel class" button under the date.
A confirmation dialog shows the class name, date and time, and reminds you that any booked members will be notified. If anyone bought a single-class pass for this class without booking a seat, the dialog says so in amber — those people get NO cancellation email, so contact them yourself before you confirm. Confirm to cancel.
Every booked member gets a cancellation email and their credit / pass is refunded automatically. You don't need to contact them separately.