You can register on www.vodacom4me.co.za and add bundles there..... that is if it works. Managed to add a data bundle yesterday via the website but it does not always work.
recently and apparently it was only added on one system and not another. I was then billed for airtime as well as the apparently free e-mail address....
Login to Vodacom4ME, go to My Account >> Services >> Modify Services.
But I agree - not sure it works properly.
Perhaps call the data help desk (155). When you call, listen to the IVR & they have a Call Back option where you push hash - this works quite well & is often quicker than waiting for an operator (at least, that what I find).
It does work, i added a bundle from the website last month, it took about 24hrs to show in the data usage/account info. section but it did work atleast.