I agree with my colleague's assessments. This is not a defense to statutory rape in NJ either. If you are charged with offense, you need to consult immediately with an experienced criminal defense lawyer licensed in GA. Good luck.
DISCLAIMER: I do not practice law in your State. This answer is provided for informational purposes only. This answer does not constitute legal advice, create an attorney-client relationship, or constitute attorney advertising.
Statutory rape is known as a "strict liability" crime. Akin to .say, speeding on the highway, there is no requirement that you "intend" to commit the crime, the act itself is a violation of the law. Your mistaken belief that the person was the age of consent or that the person misrepresented their age is not an affirmative defense.
You really should hire an attorney.