This business of exchanging drivers licenses is a common theme. They did the same to me here in the UK. They gave me a UK one but cancelled the SA one (actually stamped it in my ID book). Of course I didn't tell them I had a card license too, so I had both licenses for a while. Now the SA one has expired because you have to renew it every 5 years and I have to go there to renew it. More money for the authorities innit?