Hai, Do you want to phone lock or network lock? I think your phone is locked to network .So you can't use any network sim card. My suggestion first you should unlock your ZTE V768 phone. If you want to unlock your phone you use by unlock code. If you need an unlock code you visit http://www.simpleunlocking.com/zte-v768/rs16wp9/ . They will send the code via mail.