It can be used as long as the device uses the same technology as your carrier of choice in South Africa, has the proper frequencies and is unlocked. But keep in mind that it is unlikely that your carrier will support the device nor would they be able to offer any warranty or technical help should you have problems.
And if you buy a used device on eBay or from any other source or person, you would have no assistance either. Buying used BBs can be problematic. Please see our FAQ for an article on buying a used BB on eBay. It has some good advice on buying any used BB, from eBay or elsewhere.