You can leave your team in the My Team section of Settings.

Please note that if you are currently on Team Billing, and you leave your team, you will be immediately moved to the Cloze free plan. 

1.) Tap on More (...) in the lower right of your screen on mobile (iOS/Android) and lower left on cloze.com.

 

2.) Tap on Settings

 

3.) Tap on My Team to expand the section.