No reliable free calculator exists for modern ZTE devices locked to SFR. The only safe way is a legitimate unlock service or carrier request.
Before using any calculator, you need your IMEI. You can find this in two ways: zte sfr 101 unlock code calculator extra quality
However, unless you are a developer, stick to a pre-built high-quality calculator. No reliable free calculator exists for modern ZTE
If the prompt does not appear automatically, you can try these dialer codes: ###825*09# *983*8284# 4. Troubleshooting Tips Hard Reset unless you are a developer