Unlock iPhone 4S Verizon to T-Mobile Premanetly?

I unlocked my iPhone 4S 32G Version to T-Mobile, and I have a pre-paid plan with it. And if I update to IOS 7 it will erase the unlock an revert back to Verison then my plan is useless. Is their a way to Permanetly unlock my verison to t-mobile?

I don't see how's that possible. Verizon is CDMA and T-Mobile is GSM.

If you are outside the US, then it's possible because Verizon iphone 4s can be unlocked for GSM but only usable outside the US.

Unlocked/locked status won't be affected when updating.