This post provides Firmware Huawei E5372 Update 21.270.09.00.82 (Mobily Saudi Arabia), which can be downloaded from the link which is provided at the end of the post. Once downloaded, extract in a folder using unzip software, and process as mentioned in the respective post. Wrong firmware / software change of a Huawei / ZTE, modem / router, may dead your device permanently. While running the Huawei firmware update, it will prompt for firmware/flash code as password. You can generate the firmware code from universal master code tool.
Disclaimer : Administration of routerunlock shall not be liable in case of unknowing change of the firmware of your modem / router / MiFi. Moreover, if you want any specific firmware of related to Huawei dongle / Pocket MiFi, then leave a comment, if it will be available then will be published. All the firmware which are publicly posted at routerunlock, are free of cost and there is no need to pay anyone.