you can try mxit, use your phones wap browser and go to www.mxit.co.za/wap and follow instructions to download. It will work with MSN but not guaranteed!
You can also try Mig33, wap.mig33.com
My previous experience with MXIT is that their MSN gateway is out most of the time during the day(too busy), You won't be able to login....But I stopped using it for about 3 month so things may be changed.
Mig33's MSN connections is much better, but once again, somehow Vodacom blocked the port it was using so you need to manually change the login protocol and port number everytime, I think new version has fixed this.
Reason for me to stop use both is that I got a new phone and it comes with MSN pre-installed. Mxit/Mig33 both good chatting programs