Did you try calling Vodacom? Not sure if the iPad has baseband issues with iPads outside SA as iPhones has.
I could not get a 3G iPad 2 when I was buying (there was a global shortage at the time)... So I ended up getting the Wifi iPad 2 from Sandton and bought a MyWi device which gives me 3G over a Wifi hotspot anywhere I go (awesome thing is I can use 5 other devices to connect to the MyWi device)
One more thing, I think Vodacom and MTN is very over priced with their bandwidth, Cell C appears to be the fastest and cheapest Internet in South Africa currently...
Sent from my iPad using my fingers