I just did the whole exercise myself and thought would share with the viewers who are dying to upgrade their iPhone 4 to iOS 5 but still would want to use GEVEY sim.

What you need to know: As of now GEVEY has not released a new SIM that is compatible with the new baseband that comes with factory stock iOS 5 firmware. Hence you would have to "preserve" your existing baseband and then upgrade so that you are able to use GEVEY.

What you need to go ahead:

1. You would need to download the latest Sn0wbreeze version which allows you to custom make the stock ipsw so that baseband is preserved. You can download the latest Sn0wbreeze 2.8b8 from here

2. You would need to download the iOS 5 firmware and keep it safe before we start. You can download the firmware from here . It is 774mb and you would get a ZIP format file.

3. This is a special step that you have to do, because the downloaded ipsw would be in .zip format the sn0wbreeze wouldn't identify it. Hence you would need to change the extension to .ipsw. You can google and check how to do that depending on what version of windows OS you have. If you are having windows 7 then follow these. Go the folder you have saved .zip file --> click organize --> click folder search options --> click on view tab --> uncheck the option "Hide extenion for known file types" --> Then just rename the file with ending .ipsw instead of .zip

How to UNLOCK: Now the prerequisites are over and you are all set to UNLOCK your device. It is very easy if you follow the steps exactly. Do NOT panic at any moment as Sn0wbreeze is an excellent tool to work with.

Step 1: Execute the Sn0wBreeze exe, click ‘OK’ and click ‘Close Credits’ and click the blue next button in the bottom right-hand corner.

Step 2 : Either Drag or browse the .ipsw file which you created above. Click next.

Step 3: Click the blue next button in the bottom right-hand corner, and select Baseband Preservation Mode. You will receive a reminder about jailbreaking, ignore it and click next.

step 4: Now Sn0wBreeze will start building your firmware. It will give you the option to play PacMan, or stick to the spinner. I didn't want to get distracted hence i stayed with spinner. Totally upto you but i suggest if you are doing this for the first time use the spinner and stay focused.

Step 5: Once completed, Sn0wBreeze will place the custom created firmware on your desktop. It will be prefixed with “Sn0wBreeze”. Easier to identify.

Step 6: You are almost done, now all you need to do is follow the onscreen instructions which will take you DFU mode. Just FOLLOW the instructions including the timings.

Step 7: Sn0wBreeze will run ‘iReb’ and do somework for you which you don't have to worry at all. Click ok, and close out of Sn0wBreeze completely.

Step 8: At this stage you would have to open your iTunes and automatically your device would be identified by iTunes as in "recovery" mode.

Step 9: VERY IMPORTANT STEP --> Click "shift" + "Restore" key, to select the ipsw created by Sn0wbreeze. If you don't click Shift key + Restore (button in iTunes window) then you would NOT get the option. And ensure you select the ipsw which has "Sn0wbreeze" in its name as only this file would have your old BB preserved.

Step 10: iTUnes will do rest of the job and at the end when it reboots you are DONE. Your device is UNLOCKED with old BB so that you can use your GEVEY.

Step 11: I would suggest you remove your GEVEY while doing this as once your iPhone reboots after installing iOS 5 it would ask for activation and at that time you must just have your original sim.

Step 12: Open the SIM tray and pop your GEVEY you would always do and enjoy UNLOCKED iPhone 4 with iOS 5.

Please share your comments if you have had any problems with above steps. I just did above and am UNLOCKED.