Payments & App confusing

Can some one help on how I do payment for a sub?
cant change the username either?
App is very confusing

tag @support and/or send an email to support@trakt.tv would be your best options to get this resolved faster.

Also, a possible option is try using the actual website. It’s much more stable than any of the native apps (although the apps are getting better and better with each updated release).