Major lawsuits involving the Agency relate to investigation of violations associated with market entities' abuse of their dominant or monopolistic position; bringing the entities included in the State Register to liability for a failure to provide information to the Agency, and appeals against the Agency resolutions to include market entities in the State Register of dominant or monopolistic entities.

The most notorious case, which received extensive coverage in mass media, was a joint investigation by the Agency and the Russian Federation's Federal Antimonopoly Service (FAS) in relation to the major cellular communication operators of the RoK and Russia -- GSM LLP, Kazakhtelecom OJSC, Kar-Tel LLP, and Mobile Telecom-Service LLP (RoK) and Vympelcom OJSC, MTS OJSC, and MegaFon OJSC (Russian Federation). The investigation revealed that international roaming tariffs used by Kazakhstan's and Russia's cellular operators were overrated. The tariffs inside the CIS exceeded similar tariffs applied in the European Union by 3 to 10 times.

The antimonopoly agencies of the two countries qualified the actions of cellular operators on establishing unreasonably high international roaming tariffs as abuse of their dominant position aimed at establishing monopolistically high prices. As a result of the investigation, the cellular operators voluntarily lowered their international roaming tariffs. For instance, Kazakh cellular operators lowered their international roaming voice call tariffs by 1.5-2 times, SMS tariffs by 3-10 times, and GPRS (Internet) tariffs by 6-10 times per 1 Kb.