Most carriers will provide an unlock code for free if the phone is fully paid off and the account is in good standing. You can usually find these portals on sites like AT&T, Verizon, or T-Mobile.

Is the device completely , or is it still under contract?

Modifying your device with unauthorized software instantly voids any remaining manufacturer warranty. Furthermore, future official over-the-air (OTA) software updates may permanently re-lock or disable a modified device. Safe and Legal Alternatives to Unlock Your Phone