Tigo, like other operators, offers free incoming calls and per second billing, where subscribers pay for only what they use.
The Tigo statement said its "strong customer focus" has paid off well for the company.
It said a recent survey by market research firm Nielson revealed Tigo topped the list for best customer satisfaction across a number of factors including value for money, network quality and customer service.
"Satisfied customers bring in other customers," said Ratnayaka. "That’s why we grow continuously."
Tigo Sri Lanka's parent Millicom International Cellular S.A., is a global telecommunications group with mobile telephony operations in 16 countries in Asia, Latin America and Africa.
It also operates cable and broadband businesses in five countries in Central Ameri