First Way – Just insert the different SIM card in the modem and plug to PC E353 should ask for unlock code. Just input the unlock code and click OK to unlock your dongle.
Second Way – Some modems come only locked to its dashboard. Means you can not create any profile inside the connection manager or software of the modem. In that, you need to change the software of the modem, that is also called rebranding. You can download the latest Huawei mobile partner and install in PC to enjoy the unlocked dongle.
Third Way – You can use Huawei Code writer tool to write unlock code in your any Huawei modem including Huawei E353.
Fourth way – It is the worst way. It involves the firmware change in your dongle. In this process, if any interruption will happen in the dongle, then your modem will be permanently dead. While updating the firmware it will ask for firmware code (password), you can generate from universal master code tool.