I'm not sure if mdma would show it but they default software should have the network search function.
The best bet would be just to buy airtime and visit got to this website when you are connected with your 8ta/Telkom sim
http://onnet.8ta.com or buying it manually via the *180# menu. For you that use the sim in a modem the best bet would be the website onnet.8ta.com from the sim you want to buy the data on. Its a very handy site to buy data if you browse from that simcard. If not you can register on the site and then just log in to buy bundles after you registered.
The bundles are clearly marked Telkom Mobile bundles which only works on Telkom Mobile network and All network bundles that works when you are connected to MTN or Telkom Mobile network.