Bharti Cellular on Friday effected hefty increase in monthly rental for national roaming to Rs 99 per month from the existing rate of Rs 30. In the case of international roaming, the rental has been hiked to Rs 150 a month from Rs 60, a company spokesperson said in New Delhi. The surcharge on the roaming, however, has been reduced marginally to 10 per cent from 15 per cent, he said, adding that the new rates would come into effect from September 15. Bureau Report