The most straightforward way to unlock this device is by using an (SIMLOCK code).
Stock Huawei routers have a locked bootloader. The top unlock firmware requires an unlocked bootloader. Using the tool: huawei b311221 unlock firmware top
: Equipped with one LAN/WAN port and a standard SIM card slot. Troubleshooting & Reset The most straightforward way to unlock this device
Updating or "flashing" a generic firmware is a permanent way to remove carrier restrictions and access advanced features. HUAWEI LTE Cat.4 WiFi Router (B311-221) - wifi-stock.com huawei b311221 unlock firmware top
: You will be prompted for an unlock code. Once entered, the router will permanently accept all SIM cards. Firmware Management