Please help as I am very frustrated by our mobile network operators here in South Africa.
Be aware that WiMax services operate on a range of bands, so just having a card that says "WiMax" may not give you any operation with what is implemented for WiMax in RSA... I understand that RSA may have adopted the somewhat non-standard 2.6 GHz band for WiMax (http://www.bmi-t.co.za/?q=content/south-africa-goes-its-own-way-26ghz
), but you should check that yourself.
The common bands for WiMax operation (so far) are 2.3 GHz, 2.5 GHz and 3.5 GHz.