Important rules for your Facebook Page URL aka username
You can only have one username for your Page or profile.
You can’t claim a username someone else is already using.
Usernames can only contain alphanumeric characters (A-Z, 0-9) or a period (“.”).
They can’t contain generic terms or extensions (.com, .net). However I was able to append “com” with no problem.
Periods (“.”) and capitalization don’t count as a part of a username.
Usernames must be at least 5 characters long.
Your username must adhere to Facebook’s Terms.
How to change a Facebook Page username:-
1. Log into Facebook as the personal profile that’s an Admin of the Page you wish to change. Please do so on a computer.
Click About on the left side of your Page.
2. Click Edit next to your current Page username.
3. Enter a new username.
4. If it’s available, meets the guidelines, and you’re SURE you want to make the change, click Create Username.
Watch the full video To Change/Create Facebook Username 👇👇👇