Hello Jonny Boy,
If you want to change the name of your Facebook url, then, according to Facebook’s new rules, there should be at least 25 likes on your page, if your page is newly created. But if your page is old and after that you want to change the name even after doing once, then you can’t change it. But if you are going to change it for the first time, then you can apply for it and remember after that one chance you wouldn’t be able to change it. So choose carefully this time, which you can keep for life time.