Now i know its not walmart that denied me. I will admit that about 20 years ago when my wife and i were newlyweds we had an argument that went to far and she had a nosey co-worker decide to have her husband that was a police officer from another county push a warrant through charging me with DV. I pled the charge down to simple battery. paid my fine, went through state mandated anger management classes, completed all community services and was released off probation. I have in no way gotten into any other trouble since, not even a.speeding ticket.
I boldfaced the salient words of your description. The rest is just noise (more than likely) in regard to your situation and complaint.
If for what you pled guilty is sufficient to keep you from purchasing a firearm, then it doesn't matter if it was day 1 or day 20,000 after the offense, or that you haven't been in trouble since. Generally speaking, time does not negate the conviction. You have to go through the courts to rectify this situation (if it can be done) or it will remain in place.
Maybe the paperwork caught up with your records. Maybe you had not purchased a gun since 2009? In 2009, the Supreme Court held that the Gun Control Act’s prohibition extends to anyone convicted of any crime involving “physical force or the threatened use of a deadly weapon” against a person with whom the perpetrator had a domestic relationship--even if the crime is just plain old “assault and battery” rather than a specific “domestic violence” charge. So even if GA wasn't enforcing the Act prior to then, it should have afterwards for your simple battery against your wife, based on what you described and what I have read. That would make you a prohibited person in regard to purchasing guns and hence your denial.
As noted, get a lawyer. Maybe you can get your record expunged with the argument about how long it has been since you did anything wrong.