You CANNOT change Xfinity username yourself and moreover Xfinity violates European Union Laws by hardening account deletion.

You CANNOT change Xfinity ID username. In fact i cannot delete my Xfinity ID Account or my forum account even if i no longer need an account and don't have any billing accounts associated with my Xfinity ID account. They provide instructions via this link: Remove a Xfinity ID for a Manager, Member, or Viewer - Xfinity Support to delete the account permanently, but i have to first ask person to invite me for a viewer or member account BEFORE i can ask primary user to permanently delete account and moreover only primary user can delete accounts. Meaning they harden to even delete my forum account (even if i no longer need in the account) and i don't have option to even change that username (Xfinity ID username or forum username) and if i want to change username i now have to permanently delete account and recreate a new account again from scratch, but now they require +1 mobile phone number in order to sign up for Xfinity ID! Meaning foreign users in countries like Ukraine, Moldova or Romania can not sign up for Xfinity ID Account at all! And Xfinity Support asks me for service address that i can not provide because i don't have one and that is even when i am not Xfinity customer and don't live in U.S. at all (i never lived in U.S.)!