There does not seem to be anything in the South Carolina court rules that makes personal service, rather than by mail, necessary.  The fact that you actually received the subpoena is considered by most courts to make the service by mail good enough.A local attorney who practices criminal law can give you more definite information about what is or is not proper service, and what you can or should do if the service is not proper.  If you need to find a lawyer, you can do that at http://attorneypages.com