We will add the option to rename teams soon. Until that time the only solution is to create a new team and then move people one by one there and then delete the old one. Not convenient for now, sorry about that. Will improve soon!
Editing team names is available now for some time already. Just go to Settings - People and teams page and click on any team name to edit it in-line. Then just click enter to save the new name.
Customer support service by UserEcho