A green frog has dorsolateral ridges (a little ridge of skin) that run from the eye down the sides of the back (which look to be there in your picture, but it's a little hard to tell), a bullfrog doesn't have these. When you know to look for them they're pretty obvious in the field. So yours looks like a green frog to me and not a bullfrog.
I'm not very familiar with frogs down south though, but given the apparent ridges it doesn't seem to resemble any of the other options on the list at
Frogs and Toads of South Carolina and Georgia | SREL Herpetology You might want to go through their descriptions and make notes on how to tell the various ranids apart, then go back out and do some examining in the field

. Being familiar with key characteristics will also help you take photos for later ID where these differences are prominent. For example, a bullfrog and a pig frog can be distinguished by the webbing on their hind feet, so if you suspect you've found one be sure to clearly photograph their hind feet to examine later.
It obviously sounds like a green frog as that's what your sound byte was a recording of

. Recording what you hear can also be useful. It doesn't need to be super high quality to help, a cheap mp3 with a voice recorder can do the trick for later playback.