The farmers lobby group Grain South Africa believes AB InBev, the world's biggest brewer, has contravened one of the conditions set when the country's competition tribunal approved its $106 billion acquisition of rival beer maker SABMiller. "We are aware of the complaint lodged by Grain SA and have formally responded to the Competition Commission," AB InBev Africa spokeswoman Robyn Chalmers said. "We have, at all times, conducted our operations in compliance with the conditions imposed by the Competition Tribunal."