Methods for transmitting mobile originated requests by mobile station and systems utilizing the same

A method for transmitting mobile originated request by a mobile station with a first subscriber identity card and a second subscriber identity card, executed by a processor, is provided. A subscriber identity card is determined from the first subscriber identity card and the second subscriber identity card. A first mobile originated request is sent to a called party via the determined subscriber identity card. A second mobile originated request is sent to the called party via the subscriber identity card other than the determined subscriber identity card when the first mobile originated request has failed. The method can enhance success rate of service request.