这段程序GSM拨不通电话

  USART2_printf(USART2,"atir");/*ati初始化sim900模块  */
    Delay(0xAFFFF);
    USART2_printf(USART2,"atir");
    Delay(0xAFFFF);
    USART2_printf(USART2,"atir");
    Delay(0xAFFFF);   

    USART2_printf(USART2,"ATD13009634851;r");