I recommend you go on a Saturday. When I first inquired, they told me the person who can fill tanks is there on Saturdays. That was in Jan. 2021 though, so things may have changed. Since then I’ve just always gone on Saturdays (I have 3 CO2 tanks). This past Saturday I actually got the last of it (2.5lb); don’t know when they refill but it might be worth calling before you make the drive! Definitely worth it to check out their selection…especially if you have planted community tanks.
I realize this thread is a month or so old, but I used to get my CO2 cylinders refilled at Atlanta Beverage Control all the time, over near Stone Mountain when I had a planted tank. Good people, never any hassles and they had a walk-up will call desk.