This decision was part of a plan to reduce call costs in Africa's largest economy.
The Independent Communications Authority of South Africa (ICASA) said the costs would be cut to 20 South African cents from 40 cents from March 1.
The costs will be further cut to 10 cents by March 2016, while the fees for fixed-line calls will also be reduced over the next three years.
"As we get down to the business of regulating this sector, our beacon is to attract local and foreign investors, and position this industry as a sector of choice," ICASA's acting chairwoman, Nomvuyiso Batyi, said on Wednesday.
ICASA has said a lack of competition in telecommunications has led to inefficient pricing.
The lower fees would likely have an impact on revenue for South Africa's main mobile operators, MTN Group and Vodacom Group, and fixed-line operators Telkom SA and Neotel.
Shares of Telkom, which stands to benefit from the change in legislation, rose more than 2 per cent to 32.21 rand at 0830 GMT.
Those of rival MTN were down 0.13 per cent to 204.86 rand and Vodacom was up 0.93 per cent at 123.47 rand.