I use Waters out of Camilla GA. But Waypoint and Ward are other good choices.

One major difference between commercial labs and Auburn Extension is the quality of info you receive for only a couple of dollars more per sample. Request a complete sample that will give you base saturation and micros. The university labs are estimating CEC based on texture (which isn't totally wrong) whereas the commercial labs report actual CEC. They also give you the base saturation %'s.

If you want a deep dive into this I recommend the Kinsey Ag Soil Series podcast on Spotify and the Ag PHD podcast searching for topics like CEC, Base Saturation, Potassium, Phosphorus, Sulfur and basically anytime Neal Kinsey is a guest.