New Delhi, Jan 5 :    New Delhi, Jan 5:  Mahangar Telephone Nigam Limited (MTNL) will launch its cellular service, based on global system for mobile communications (GSM) technology, in Delhi on January 31 and in Mumbai on February 28. Communications minister Ram Vilas Paswan today unveiled the schedule for rollout of GSM mobile phones from MTNL in the two cities and promised competitive air-time rates. The registration in Delhi for one lakh mobile cellular phones will start on first-come-first-served basis from January 15 and the service will start on January 31. In Mumbai, the registration will begin on February 15 and the service will be launched on February 28. 'The tariffs will be announced after taking approval from Trai. Tariffs will meet people's expectations,' Paswan said. 'The MTNL tariff will force other cellular operators to bring down the air time cost for consumers which they had promised. While migrating to national telecom policy they had promised the government to bring down air time cost. Our tariff would force them to keep their own promise,' sources MTNL said.