In the world of feature phones, the Samsung Guru Music 2 (model number SM-B312E) remains a legendary device. Known for its durability, impressive battery life, and dedicated music keys, it is still widely used as a backup phone or by those who prefer simplicity over the distractions of a smartphone.

If you bought a second-hand B312E or switched carriers, this pop-up appears because the phone is "subsidized" to one network. The manufacturer (Samsung) and carrier don’t want you switching to a cheaper competitor without paying a fee.

If you have forgotten a custom password and are locked out of the phone's functions, you can perform a master reset to restore factory settings. This will delete all messages, contacts, and media stored on the phone's internal memory.

Unlocking a when you’ve forgotten the SIM lock password can be frustrating, especially since this classic feature phone doesn't have the "Forgot Password" options found on modern smartphones. However, you can regain access using master reset codes, network PUK codes, or specialized flashing tools. 1. Default Passwords and Master Reset Codes

Many users never set a custom PIN but suddenly see the request. Try these default Samsung SIM lock passwords first: