Online unlock services charge for SIM unlock ($15–$30). Then they charge again for band unlock ($10). Then again for firmware update ($20). With custom firmware, you pay nothing (open source) or a small donation to a developer—and you get everything unlocked.
: The interface for managing SMS and running USSD codes (for balance checks) is often more stable and responsive in the generic firmware compared to bloated carrier versions. Connectivity and Stability zte mf286c unlock firmware better