Without prior notice, phone card vendors last week slammed a 10 percent increase on calling cards for Zain, Comium and Africell networks. Only Tigo's card rates remain the same.

Natcom said in a press release that the increase violates the Telecommunications Act 2006, which makes it mandatory for all public telecommunications operators to submit written proposals for tariffs to the commission.

The commission noted that under the Act, it has 30 days to consider, modify and approve tariff proposals submitted to it by operators, and consumers also have a right to comment.