You can't remove SIM lock by upgrading to Froyo 2.2 from stock 2.1 ROM . But, you can use the features of the newer version ( Froyo 2.2) . You can remove SIM lock by using unlocking method. A lot of possible ways available for unlocking phones . Among all, using unlock code is one of the legit way to unlock your ZTE Blade from your locked network. You can unlock your phone by using software/from your Network carrier/using free instructions/from any of the third-party service providers like Onlinegsmunlock.com . Note : Unlock service cost will vary from one provider to another. It depends upon their service. To get the code from online service, you have to mention your country and network to get the unlock code from them. So, it is not possible to remove SIM lock by just upgrading stock ROM to any custom 2.2 ROM.