You do realise that this is not allowed on MTN's network???
"In terms of the current regulatory regime in South Africa, please note that these tariffs and the MTN GPRS, GPRS+, EDGE or 3G technologies may not be used to transfer or generate Voice over Internet Protocol (VoIP) traffic. Should it be found that VoIP traffic was carried over the MTN network using these tariffs or technologies, MTN reserves the right to cancel the agreement that you have with MTN, with immediate effect. You will also be charged retrospectively at R21.93 per Megabyte (VAT excluded) for any VoIP traffic transferred by such means."
Before long all operators, Wireless and/or cabled, will have to face up to the fact that they are data carriers and adjust the business model appropriately. The difference between Voice and data is long gone and new technologies/protocols are emerging almost daily. They will be chasing their tails and wasting money just policing the traffic for the sake of pretending to be Voice Carriers.
Look at the gadgets hitting the market in the past year, Cellphones, Media Players, TV's, EBooks, Laptops, tablet PC's even cameras all now connect to the internet by 3G, WiFi or Ethernet and carry some combination of Voice, Video, Data, Media etc. The latest gadget, iPad, carries the lot in one box.
Lets drop the old paradigms and get with the 21st century.
What we need is a bandwidth allocation and a Pipe. Let us allocate that bandwidth between, voice, data and media according to our needs and allow us to use it on any network.
After all they do call themselves Network Operators, it is time they started acting as such and dropped the analogue mind set that makes them behave as a telephone operators.
edit: I was surprised that the current survey didn't ask about VoIP, every one I know is useing it in one form or another, and in some cases got ADSL just to use voice.