Elisa, Finland's second-largest telecoms operator, saw an 18% drop in first-quarter profit, caused mainly by billing problems and cheaper tariffs, an Associated Press report said.
Net profit from January to March was €40 million (US$63 million), down from €49 million a year earlier, Elisa said.
Net sales also fell, by 3%, to €367 million, the report stated.
Earlier this week, the company said revenue would be hit by €21 million because of lower mobile connection tariffs and revenue adjustments caused by delayed customer billing.
Elisa gave a positive outlook, saying that its mobile subscriptions had increased by 22,000 in the period to a total of 2.7 million, with fastest growth in 3G connections.
The company claimed it is still the market leader in broadband subscriptions with an increase of 13,000 in the period, or 2.5% more than a year ago.