Starting in 1993 using an analogue AMPS (Advanced Mobile Phone System) platform, it now has HSPA and mobile fourth generation LTE technology.
The firm had invested more than 500 million dollars in infrastructure.
Mobitel said it now covers Sri Lanka's North and Eastern areas where a war ended in 2009.
"Our subscriber base spans from businessmen to farmers in the furthest corners of the island," Mobitel chairman Nimal Welgama said in a statement.
The firm said it had opened 'contact centres' in Mullativu in the north and Sooriywewa in the south creating ICT based employment opportunities for the youth in those areas.