If there is a method of changing the name, I would not do it. You may choose to just copy (option 3 from WRKUSRPRF) to a new profile using the new name and disabling the old account until you are confident the old account can be deleted. You may also was to display any objects the the original account owned (Option 12 from WRKUSRPRF) and change the owner (option 9) to the new account.
There may be additional access set up involved (e.g. DIRE, DSTL, etc.) but should be quite simple to set up.
I forgot to mention…my suggestion above, does not include IBM supplied accounts.
Renaming or changing a user profile name is not allowed. As started above, copying the profile is your best option. To verify all objects and authorities the existing profile has, enter the command DSPUSRPRF userprofile *ALL and enter thru the screens.
For cases where DIRE, DSTL, etc., are involved, also review the Rename Directory Entry (RNMDIRE) command. <b>Especially</b> review and understand the help for the command.