If you have a premium GF membership (Company Annual, Company Lifetime, Supporter Annual, Supporter Lifetime ) you will be able to change the country flag of your profile.
Sometimes the IP to Country system the forum software is using is not so accurate and do mistakes. Also if you travel a lot or use different computer, IPs or VPNs you can setup a country that will always be shown in your profile.
To do this follow the steps in the following picture:
If you need help don't hesitate to PM me.