Siyanda, if memory serves, is a one-way satellite service provided by MWeb. The service works together with a dial-up or ISDN line. The land-line is used to transmit outgoing data, while the satellite receives incoming data. In the majority of cases you send a lot less data than you receive, so transmitting at modem speeds is not a big problem, while receiving at satellite speeds is a very significant and noticable improvement. If I remember correctly in the early days Siyanda was burstable up to 1Mb/s.
I'm not sure whether Siyanda is still in operation, but I've heard of at least one or two companies who provide the same service to this day.