China's mobile-phone users at the end of April rose to 583.5 million, up by 8.9 million from end-March, data issued by the Ministry of Industry and Information showed.The growth in the number of mobile users slowed in April compared with the net additions of 9.4 million in March, according to statistics issued on the ministry's Web site Wednesday.China's mobile-phone users grew by a record 9.5 mil