Question Problem in Result SerialPort & AT COMMAND USSD

[ak1_2004]

Hi
I have a problem in my project .
please see this code and answer me how to fix this problem !

i can not get result of USSD or other AT Command When Sending DATA !
For Example :

[LEFT][COLOR=#333333][FONT=Consolas]Public Sub SendUssd(ByVal ussdcode As String)[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]    With SerialPort1[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]        .Open()[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]        .DiscardInBuffer()[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]        .DiscardOutBuffer()[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]        .WriteLine("AT+CUSD=1,""" & ussdcode & """,15" & Chr(13))[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]        System.Threading.Thread.Sleep(15000)[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]        Dim result As String = .ReadExisting[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]        If InStr(result, "OK") > 0 Then[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]            MsgBox(result)[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]         End If[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]        .Close()[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]    End With[/FONT][/COLOR]
[COLOR=#333333][FONT=Consolas]End Sub[/FONT][/COLOR][/LEFT]

Or
i using of AT+CMGS to send SMS after Send it i can not Get answer +CMGS=[NUMBER] !

please Help me !