Trading at Vodafone worsened in the third quarter as falls in customer usage in Europe pushed organic service revenue at the world's second largest mobile operator down a worse than expected 2.6 percent.
The plunge in group organic service revenue for the three months to December 31 marks an acceleration from the 1.4 percent fall recorded in the second quarter and a forecast of a fall of 2.4 percent.
The fall in the second quarter marked the first fall in the key industry measurement since 2010.
The group, led by Vittorio Colao, was hit by fewer customers making calls in southern European markets such as Spain and Italy, a slowdown in Germany and Britain, and weaker growth in emerging markets such as India.
The group kept its outlook unchanged for free cash flow for the year, after it nudged it lower at the first half results in November.
(Reporting by Kate Holton; editing by Paul Sandle)