VS 2010 read SMS from sim (usb 3g modem)

hi guys..

i'm having trouble in reading sms...

in hyperterminal:

AT
-ok
at+cmgf=1
-ok
at+cpms?
-+cpms: "SM",11,50, "SM",11,50, "SM",11,50
OK

my vb.net code in reading SMS..

serialport1.writeline("at+cpms=""SM"")

or

serialport1.writeline("at+cpms=" & chr(34) & "SM" & chr (34))

also tried this

serialport1.writeline("at+cpms=")
serialport1.write(chr (34))
serialport1.write("SM")
serialport1.write(chr (34))

always returns ERROR

what could possibly wrong with my codes? thanks for your help guys