This is related to cell phone towers and your phone’s location services accuracy instead of facebook actually.
I’ve seen this happen around Lexington showing people as posting from “Catnip Hill.” There is in fact a cell tower located off of Catnip Hill Road in Nicholasville (city next to Lexington for those outside the area) but that tower provides that location information for people who are posting while on that cell tower’s network … even when they are in fact in Lexington. “Little Georgetown” is another mistaken location people in Lexington often get.
Basically to have a shot at getting this changed, you have to improve the accuracy of the phone’s location services in order to possibly get a more accurate location. Scroll down to “Improve GPS accuracy” on the following page and see if these instructions help (iOS 8):
http://support.apple.com/en-us/HT203033
This may or may not fix it. If it does end up helping now but then later you have a problem again, you may want to restart your phone. I’ve seen phones that haven’t been restarted in weeks hold onto old location information longer than they should.
If you’re posting from your computer then it has to do with location information being sent by your ISP (or your VPN) and I really don’t know any easy ways to correct it from that or the answer is going to be more specific to those services.
Good Luck!