I've little idea... Gauteng you say? Let me research this a bit...

Well, if it is in South Africa, it may be either of one of these:

Rana Angolensis - Common River frog

Ptychadena mossambica - Broad-banded grass frog

Or it could be an Indian Bullfrog. Unlikely due to how far away India is, though.
I'm honestly not sure. Perhaps someone with more experience will be able to truly identify it.
A picture of the snout/face of the frog would be useful.