You pay in-state tuition and fees at South Carolina public colleges and universities no matter how long you have lived in the state. If you are the child of a parent serving on active duty outside South Carolina, you need to be using transferred VA education assistance, and once that assistance runs out you are charged out-of-state rates unless you can claim South Carolina residency.
Tell the admissions or residency office at the South Carolina public institution you are attending that you qualify for the military in-state rate, and give them your service or VA education benefit documentation.
Your DD214 or current military orders, your VA education benefit certificate of eligibility if you are using transferred or personal VA education assistance, and proof that you live in South Carolina.