SC's agricultural extension agency is administered by Clemson U, with offices in each county. We've used them for soil testing
numerous times, with good results. When we ran into some strange results, we found both the local agents and experts at Clemson were more than willing to discuss the results and recommendations with us. Interestingly, they didn't always agree with the printed recommendations on the testing results.
After you do the test, I think some of the recommendations were computer generated, so it never hurts to discuss them with a real, live person.