CREATE TABLE table_19246_1 (carrier VARCHAR(255), frequency VARCHAR(255), launch_date__ddmmyyyy_ VARCHAR(255))
When the launch date is 14.09.2005, and the frequency is 900mhz and 1800mhz, how many carriers are there?
    
SQL: SELECT COUNT(carrier) FROM table_19246_1 WHERE frequency = "900MHz and 1800MHz" AND launch_date__ddmmyyyy_ = "14.09.2005"