Apple have confirmed that next week 36 more carriers will receive LTE support. Although they didn't confirm the names of the carriers we have reason to believe the Vodacom and possibly MTN are on that list. Vodacom have suggested that they will open their LTE network to iPhone 5 uses by the end of January.
Vodacom and MTN have both enabled their LTE networks to by used by people with compatible devices. CellC have opened up a trial to test their LTE network but have stated that they won't completely open it until the Department of Communication have released spectrum specifically for LTE.
If you are on CellC I wouldn't be too concerned about this as CellC has a world class HSPA+ network which is only marginally slower that Vodacom and MTN's LTE networks.