The company, which offers low-cost international mobile calls to migrant communities across Europe, has not previously used a PR agency in the UK.
Fleishman-Hillard director Sophie Scott said: ‘Lebara want us to help in its overall ambitions for growth.’
Lebara is one of Europe's fastest growing mobile virtual network operators. Its revenues rose 53 per cent to €565 million last year and its profits were up 139 per cent to €21 million.
The network was founded 10 years ago by its chief executive, Sri Lankan refugee Yoganathan Ratheesan, with two partners.
In October the company signed a contract with Nokia to deliver handsets with Lebara SIM bundles to its customers worldwide.
This is the first time that a mobile telecoms operator serving migrant communities has agreed a global deal with a handset manufacturer.