The MTN sharelink B683 and 2GB of data is currently R189 on a 24 month contract.
The Galaxy SIII is R399 on a anytime 200 package for 24 months and includes 75mb data the first 12 months.
Galaxy SII is now R269 instead of R299 for the 24month package.
As mentioned before I do not work for them. If you need more info please contact MTN or go to a local store near you.