Your MiFi is not turned off when it is blinking green.
Blinking Green normally means that your device is 4G LTE connected and transferring data. As opposed to a solid green light which means that your connection is active but no data is moving across the device.
Granted every device is a little different. Post your MiFi model number so we can look up the User Guide and confirm.
Let's ensure your MiFi device is not incurring any unexpected data usage! As John suggested, please provide the device model name of your MiFi hotspot device so we can provide you specific steps. Also, have you tried locating and holding down the power button of the device to ensure it's powered off?
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