Lumia 521 - Unlocking Codes For Nokia

Websites like UnlockBase and Cellunlocker.net provide codes for a fee. These services typically require your phone's IMEI (find it by dialing *#06# ).

If you are the original owner and the phone was on T-Mobile , you can still request a 20-digit unlock code through their support channels. Unlocking Codes For Nokia Lumia 521

You can often trigger the code entry screen without a foreign SIM card by dialing ##7820# on the phone's dialer. Websites like UnlockBase and Cellunlocker