Hello, am sharing with you this solution for only the specified sim / usim can be used on this device. You don't have to worry about using credits bought into dollars since you can do it yourself. You only need a code writer, an unlocker and you are done. Simply connect your modem on your on your computer and you will be done.. See full tutorial here https://kwsadams./2014/10/06/huawei-solutionfix-for-only-the-specified-simusim-card-can-be-used-on-this-device/