A common misunderstanding as to how the Internet actually works, is to assume that the speed of your ISP connection [e.g. Vodacom's HSDPA] is the speed you would get to anywhere on the Internet, which is simply not the case.
Simplistically, the Internet is a collection of links and routes that define possible paths to get from one point to another point, and more importantly the bandwidth or possible speed of these links varies as well as fluctuates according to how much bandwidth is being used at any given time by [one or more] users.
My point is that first testing the speed between your PC and your ISP is where one should start, i.e.
http://speed.vodacom.co.za/, and if that speed is within your preferred range, then bother with other relevant speed tests, and if you are trying to test the speed to a site [e.g.] in the USA, then there probably isn't much point in running a speed test outside of the USA as it is highly likely that that would travel a different route where the speed of links is not going to be the same.
There is a lot more to this that could be said, e.g. traffic shaping, etc.