To close a Channel, you'll first need to login to BigMarker. Then go to your personal settings and click Close Account:
Once you choose the Channel to close, click the Close Channel. this point you will be asked if you would like to assign another organizer or subscriber to continue as the administrator. Or you can continue to close the Channel.
Once you delete the Channel, it nor it's subscriber information can be retrieved later. As a result, you may want to downgrade the Channel to use at a later date.