In my experience, the only way to bypass the configuration password is to do a firmware upgrade. in the process of upgrading the firmware you will have the option of restoring to default configuration. If you do this you will loose the current configuration that's on the device. The default password is gl200.
Are you sure the password was changed? GL200 doesn't respond to SMS commands via SMS, it will acknowledge the command via GPRS.
Do you have the configuration tool application for the device that matches the device firmware version?
onPoint GPS Tracking & Fleet Management