There is
no same-day deadline — you can change or cancel right up until the session starts. What it costs depends on how close you are:
To move it: tap
Change Session and pick another time that same day. The credit moves with the session, and no fee applies. You can move into any time that day that has not started yet.
To drop it: tap
Cancel. More than
2 hours before the session it’s free and the credit comes straight back. Inside 2 hours it’s a late cancellation, and you choose:
keep the credit and a
$20 late-cancellation fee applies, or
give the credit up and pay nothing. On an unlimited membership there’s no credit to keep, so a late cancellation is simply the
$20 fee. Once the session has started it can’t be canceled.
Full walkthrough:
How to Cancel a Session.