Connecting 3g dongle usb to raspberry pi

I have an 3g dongle usm modem,I tested on windows works correctly
I tested on raspberry pi,using sakis3g software i got an error like
Modem responded "ERROR" while checking for PIN
I searched in google and try almost solutions but it does not work
I tested sending sms using gammu on raspberry pi and works correctly
sends sms without any error
but only internet connection has error