Each gym has an "Account Owner," the person who initiated the sign-up process with btwb. Only the gym's Account Owner will be able to change a gym subscription. If you aren't sure who the Account Owner is for your gym just visit the gym admin page to find out.
Once you are in the admin console you will need to select the "Settings" tab on the left hand side of the screen, followed by the "subscription" tab. You can only cancel your subscription via the web.
The subscription page will allow you to view, edit, and cancel each of your subscriptions. Select the Members Pay subscription plan to end your Gym Pays subscription and shift payment responsibility to your members once the current billing period is complete.