My iphone was unlocked when it is 1.01, after that, I upgraded my phone all the time.
Now my phone is 1.13, and worked perfectly(unlocked, has installer and many 3rd party apps). However, its firmware version is 4.02.13_G, which should belong to 1.12.

Now my question is how can i safely upgrade my firmware to 4.03.13 and keep my phone unlocked?

thanks million times