Telkom uncapped is currently the cheapest, but is a nightmare if you want to download torrents during the day or ever want to play online games during normal being-awake hours.
Best will be to take the Telkom simple plan uncapped ADSL month-to-month package, where you get a free modem and installation. If it does not work for you after a few weeks, cancel the telkom ISP and move to someone else. Since you can keep the free telkom modem, you can get another ISP without buying a extra Modem, or if you go to someone like MWEB, you get another free modem.
Long story short: Telkom is cheapest, but they shape international bandwidth at the moment. Otherwise, go for MWEB directly for the free router, or any other ISP with free stuff.