Changing a Discord username is similar to changing the username on other messaging platforms like Telegram. First, as mentioned earlier, head over to the ‘My Account’ section and click on ‘Edit’ next to the current username. Next, enter the new username on the screen, enter the password and click on ‘Done.’ This will change the Discord username, which will be visible to other users on the platform. One thing to note here is that Discord allows multiple people to have the same username, except it assigns a unique four-digit number to identify them.
To change the email address via Discord for mobile, head over to the ‘User Settings’ section by tapping on the avatar at the bottom right corner, open ‘My Account,’ and tap on ‘Email’ to enter the new email address. If users face any issues with changing their email address, they can contact the Discord support team. On the other hand, if users want to change their Discord username via mobile, head over to the ‘My Account’ section and tap on ‘Username’ to edit it and save the new username. Discord mentions that “usernames changes are limited to 2 an hour” on the official support page.
Source: Discord 1, 2, 3