(e.g., a SIM from a different carrier) into the modem.

offer remote IMEI-based unlocking for a fee, claiming compliance with carrier guidelines. Google Play Security and Risks

The Huawei B312-939 is a popular 4G LTE router distributed by various network providers. It is often "locked" to a specific carrier's SIM card. Unlocking the device allows it to accept SIM cards from any compatible network provider, offering users the freedom to choose their data plans and use local SIMs while traveling.

To unlock your Huawei B312939, you'll need to obtain an unlock code, which can be generated using a free Google verified code calculator. Here's a step-by-step guide: