Change my usename KoBoToolBox

hello all,
i have a problem with my KoBoToolBox account. i want to change it. the last account username is xxxxxxx and i want to change it to yyyyyyy.
your help please

Welcome to the community, @NRC_TANG_IM! Please be informed that the system does not allow you to change the username from one name to other. But you always have an option to create a different username whenever needed. If you then need to delete your existing username please reach out to support@kobotoolbox.org.