If your carrier denies your unlock request (for example, if you bought the phone used from someone who still owes money on it), you can use third-party IMEI unlocking services. These services work with database insiders or carrier employees to officially whitelist your IMEI in the manufacturer's server database. While you have to pay for this service, it is a permanent, factory unlock that survives software updates. 3. Use a Hardware SIM Interposer (e.g., R-SIM)