You will find hundreds of sketchy Google Drive links. Do not use them. Here are the legitimate methods.
If you're unable to unlock it through codes, some tech-savvy users opt for custom firmware. huawei router b311221 unlock firmware exclusive
Most online unlock services provide a code generated via Huawei's database. However, the B311221 uses a rolling code system. By the time you get the code, the router's internal clock has moved on, making the code useless. This is why firmware unlocking is the only permanent solution. You will find hundreds of sketchy Google Drive links