So at first glance, Facebook's policies on name changes look fairly simple. Their help page on changing your name states: "Keep in mind, you can only change your name every 60 days." The Facebook Name Standards page says: "The name on your profile should be the name that your friends call you in everyday life. This name should also appear on an ID or document from our ID list." *
However, real life indicates that it can be a lot more complicated than that. One friend of mine, Christina, said "I've never changed my name before on Facebook (in the 8+ years I've been a member!) and they wouldn't let me change my name when I got married, even when I changed my relationship status to married. I had to send them a picture of my ID." Another friend told me that she wasn't allowed to change her name because her married name is the same as that of a celebrity's.
This doesn't line up with what Facebook says might be a reason you can't change your name:
"You may be having trouble changing your name if:
- Your name doesn't follow our name policy
- You changed your name in the last 60 days, or you tried to change it too frequently
- You were previously asked to confirm your name on Facebook
- Your name doesn't exactly match the name that appears on something from our ID list"
This is a little bizarre, particularly because we all know that one friend or two who has a name on Facebook which is CLEARLY false (usually involving some form of "danger" or "goddess" or the equivalent) but hasn't had any trouble with it. It doesn't seem like Facebook is altogether good about forcing these standards equally.
Facebook does have a page where you can upload your ID and explain why you're changing your name, over here - https://www.facebook.com/help/contact/1417759018475333
*Sidenote, there can be many other bad unintended consequences of Facebook's name standards, particularly for Trans* people and people attempting to get away from abusers or stalkers. You can and should go read about those over issues and what Facebook has done to address them over here: https://www.theguardian.com/us-news/2015/dec/15/facebook-change-controversial-real-name-policy