There is a plugin that I use called ‘username’ just search from you’re WP-Admin Plugin Search and type ‘admin username change’ & username & a bunch of other Admin & User Username Plugin Change Plugins will appear. I cannot give you the full answer if you are looking for 3 fields eg: – Username
– eMail
– Phone #
Though I suggest finding the plugin that wull allow you to change usernames for users & admin from this search (which do show up), and after choosing find a coder who can add the extra lines of code to the Plugin.
P/S – Searching Google for a Username Login Changer Plugin would also benefit in finding the right one (simplest one for you’re needs) to ‘modify with the required PHP code’ and can be posted here if there is no a less complicated PHP only MOD someone can help you with wi/out a plugin. This is just from my similar multi-login type experience.