I've asked the customer reps on two separate occasions. One told me the 800 and the other 900MHz. So i took myself to the Telkom shop-the gpo one(looks weird. Too much space) to buy a 4G ready sim card and to settle the matter on the frequency. They told me it was the 800MHz but they weren't very sure.
I suspect it might be the 800 for one reason: In my area we always got a very weak 3G signal. This was because they were using the 2100MHz. However, over the last 1 week the 3G signal has really improved. I'm guessing they have re-farmed some lower frequency-most likely the 900-to be used for 3G. If i use the old modems(Huawei E220) which only supports 3G on the 2100MHz, i still get a very weak 3G signal. If i use my phone which supports 3G on the 900MHz, i get good reception.
So the 800MHz will be used for 4G while the 900MHz will be used for 3G. This was the set up i was expecting in the beginning; similar to Safaricom and Airtel. I could be wrong.
Their 3G is really good by the way. On YouTube, videos are loading in 1080p by default. I'm also able to stream IPTV without any buffering. All these over the 2.4 GHz WI-FI extender connection(I only get good Telkom and Airtel coverage in one spot in my house. So i have to use a wifi-extender to boost the original wifi hotspot).
I've actually shelved my plans to get the postpaid Airtel bundle.