Even if you could remember the name of your probation officer, there is no guarantee that he/she is still employed by that office. Chances are, if you call the probation department and provide them with your name and date of birth, they will connect you with someone who can give you the proper guidance of how to "clean up" your account.
I do not practice in Georgia, but rather in Nashville, TN. Your question would be better posed to a Georgia attorney but I would recommend contacting the Court Clerk's office in Dekalb County if the probation office is not helpful. Probation may collect the fines and court costs, but I would imagine that the court clerk would also know the amount owed.