SAO PAULO, Aug 13 (Reuters) - Oi SA, Brazil's largest fixed line telecom company, posted on Monday a lower net loss in the second quarter helped by lower expenses.

In a securities filing, the company posted second quarter net loss of 1.258 billion reais ($323.93 million), 70 percent lower from the same period a year ago. ($1 = 3.8836 reais) (Reporting by Carolina Mandl)