I say best solution for this thread:
R10 p/GB topup . Done.
Do the calculations, it will be better than "uncapped" , because if i use 30GB, i pay R300, if i use 70GB* i pay R700 vs. -always- paying R700 .
And then they might even lift the speed restriction too...so if you download 30GB @ 4 mbit/s you still pay R300, if you download 300GB, well then it's R3,000 for you (which is right about what a 4 mbit/s uncapped account would cost).
*Assume 70GB is the practical max you will get out of a 384 kbps line if you were to download 24-7 at an acceptable speed. Theoretical max would be more, but we know it's not really attainable (you are going to get slowdowns and you are going to stop a download to browse or to search or something).