Here's how you can change your PlayStation username for free
The much-wanted feature that PlayStation users have been longing for, like forever. The ability to change that annoying username that you decided to go with in a hurry to play your beloved games. However, yes there are some catches, first there are some complications related to the software side of the console, as not all games might support it. Second, only the first change is free and you have to pay additional charges for all the next changes. Each name change after the first one will cost you $9.99. However, if you are a PlayStation Plus subscriber it will only cost you $4.99 for every time you decide to change your username.
Sony was still kind enough to give you access to your old usernames, they will always belong to you and you can revert back to any one of them at any time you want. You can also display your old username with the new one for 30 days to familiarize your PSN friends. It's a good thought on Sony's part as it claimed in its FAQ.
You will either need access to a browser or a PS4 console to change your username. On the web just log in to your PlayStation Network account and click the edit button in the menu bar of your profile.
To change your username from your PlayStation 4, go to Settings -> Account Management -> Account Information -> Profile -> Online ID.
Sony was also kind enough to release a list of games that fully support the change, have minor known issues or have critical issues. In extreme cases like with critical games, you can lose access to your progress, your leaderboards or payed D.L.Cs. So, just inspect before using the feature that your game supports it or not.