VS 2010 send and receive sms usb 3g modem (sun, gobe, smart)

hi.. i am doing my thesis. I need to send and receive message using vb.net. my device is sun broadand ZTE 3g usb modem. i am having a trouble in sending sms. i tried my usb modem in hyperterminal and it works fine. i sent and receieved sms. but in my windows application doesn't. here is my code and design. can anyone help me with the error?.. thanks

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