I just got a notice from Aafes/NCO about intent to garnish wages. Does anybody have experience with this, specially SC residents? Is this possible?

If they have a judgment against you, yes they can.

Generally you don't get a notice of intent to garnish wages. So you need to determine exactly what you got. Sounds to me more like a dunning letter then anything else.

Before they can garnish wages, they first have to file suit against you, in which case you will get a summons notifying you of the suit. From there a court has to award a judgment against you for the amount owed. Only after that happens can the plaintiff obtain an writ of garnishment which is then served on your employer. The first you will hear that such a writ has been served is from your employer.