You can change your username once every 30 days. Changing your username will also change you default shop name, therefore changing the URL with which your customers can see your Products.

If you choose to change it, your old username will not be removed and it won't be available for other users, instead we will redirect the traffic from the old URL to the new one (your new shop name).

If you wish to get your username back, you can by changing it once the delay period is passed.