Mobile VoIP works with a cell phone’s 3G or LTE service to send voice calls over the Internet and via an Internet Telephony Service Provider. Mobile VoIP phone users and especially smartphone users can benefit from lower costs when calling, texting or using other common smartphone services. VoIP software like Skype and Google Talk are widely seen as a threat to the revenues of traditional cellular operators in South Africa as it bypasses the voice networks and so is not billed by them. Mobile VoIP dialer programs are available free of charge and enable users to make free VoIP calls when they are connected to the Internet. In a bandwidth rich environment calls effectively become free, and even in a bandwidth starved environment like South Africa, VoIP can save broadband users a great deal of money.
Eg. With a common South Africa 1 GB HSDPA package of 50c per Megabyte. VoIP programs like Skype use in the region of 500 KB per minute, which means that call costs to other Internet and Skype connected mobile phones can be as low as 25c per minute (Source: http://mybroadband.co.za)