Vodafone, one of the world's largest cellphone companies, says third-quarter revenue dropped 4.8 percent as conditions across an economically struggling Europe remained challenging.

The decline in organic service revenue — excluding currency fluctuations and mergers and acquisitions — was biggest in southern Europe. Things were brighter in emerging markets, with India posting revenue growth of 13.2 percent.

The company did not report earnings for the period.

CEO Vittorio Colao said Thursday Vodafone will respond "through on-going improvements to our operating model and cost efficiency." He has introduced a 7 billion pound ($11.4 billion) investment program to improve service.

Vodafone agreed last year to sell its stake in a U.S. venture to Verizon for $130 billion in cash and stock — one of the biggest deals in corporate history.