The operator of the “au” mobile brand, one of Japan’s top three carriers, said Saturday its customers are facing difficulties making calls and connecting to the internet as a result of nationwide network trouble. KDDI Corp. with some 60 million au customers, said the disruption started at around 1:35 a.m. and work is under way to restore services. The cause is being investigated. KDDI said users of its low-cost service UQ Mobile brand are also experiencing connection issues, as are those who use its lower-priced wireless service plan under the “povo” brand. The company apologized for the incon…