Cellular Operators Association of India (COAI) today criticised the Telecom Regulatory Authority of India (Trai) order for slashing roaming charges, and said the move could lead to increase in basic tariffs.Terming Trai's order 'distressing and disappointing', COAI said the sharp reduction in roaming tariffs was "unwarranted", and this could have an adverse financial impact for the industry to the tune of Rs 800-900 crore."The micro-management of tariffs for value-added services like roaming would leave service providers with no choice but to review their entire tariff structure in order to maintain the sustainability of their businesses," T V Ramachandran, director general, COAI, said in a statement.Reacting to the Trai decision, Manoj Kohli, president, Bharti Airtel said: "We believe the policy of forbearance of mobile tariffs, which has been followed, has worked extremely well and has enabled market forces and competition to provide the best value to customers."We believe that a selective departure from the policy is unnecessary and unwarranted particularly when certain services are currently being offered below cost."Reliance Communications declined to comment, but sources in the company said the impact of the order would be only to the extent of Rs 18-20 crore.Trai cuts charges, roaming to be cheaper