Up until last month it wasn’t easy to change your username (aka Facebook Page URL) after it had been set as you had to contact Facebook. But now Page Admins can change their Page username in the Admin panel IF you have less than 200 Likes. You can only do this once though so make sure you have the username you want. Reasons for changing the username of a Page might include a spelling mistake or company/organisation name change.
To change the username of your Page go to http://facebook.com/username or Edit Page/Update Info/Username/Change username.
Furthermore, restrictions on changing the Facebook Page name - name displayed at top of Page - have now been eased and as long as you have less than 200 Likes you can amend the name as many times as you like. Again, you might want to do this following a business or organisation name change.
To change your Page Name go to Edit Page/Update Info/Name.