Cellphone giants MTN and Vodacom are taking Icasa to court on Tuesday over the communication regulator's plans to slash mobile termination rates.

The two companies approached the High Court in Johannesburg on an urgent basis to stop the Independent Communication Authority of SA (Icasa) from implementing a regulation on mobile termination rates.

Termination rates are fees companies charge each other when calls are made from between them.

The rates were expected to come into effect on April 1. MTN and Vodacom wanted the court to permanently scrap the regulation.

The two said attempts by Icasa to set termination rates for 2014 at 20c for them and at 44c for the others was unlawful on a number of grounds.

One of the grounds was that the figure of 20c was arrived at irrationally and that the 44c rate meant for smaller players was not based on cost.

Icasa in its head if argument said the rates had driven up cost to consumers, making South Africa one of the most expensive places to use a cellphone.

The national regulator said the 20c rate was justifiable according to an independent expert and that the cost was not what determined the 44c calculation.