Update unlocked iPhone 4 to new iOS?

[Nick]

My girlfriend is getting an iPhone 4 from Ebay that is unlocked so it can work with her StraightTalk SIM. She wants to update to iOS 7 when it comes out Monday. We won't know till tomorrow if it was done by a 3rd party or legally through the carrier. If it was by 3rd party, can we still update the IOS version without losing the unlock?

[Unregistered]

If the unlock is a temporary one...when you update the phone's firmware....there are chances that the network lock may get returned.If the unlock is a permanent one...then the network lock will not roll back.I suggest if the network gets locked during the update...you can avail the permanent unlock from Unlock-zone.com and remove the network lock using their remote unlock service for you iPhone 4.