How To Activate FaceTime On Unlocked iPhone 4 Using MiTime

Users who are using an unlocked iPhone 4, on unofficial carriers (such as T-Mobile in the US) will find that FaceTime is no longer working. For those of you who are looking to fix this problem and activate FaceTime calling after unlocking iPhone 4, MiTime is a Cydia app which costs you 5.99 USD.
The app activates your iPhone anywhere in the world by sending 2 international SMS messages, so make sure you can receive international SMS by visiting this test site. The developer, the same guy who gave the Cydia fix for push notifications has mentioned on his site that the international SMS is what costs the app so much, and there is no way to avoid that.
You cannot buy the app via Cydia, only through the developer’s website using PayPal. The authorization should be done later on your iPhone before you install MiTime, by entering the same number that you entered on the website in your device. Note that MiTime will not run on unauthorized devices, so purchase your copy before going ahead.
Here are the steps to activate FaceTime on unlocked iPhone 4 (taken from the developer website):
1. Jailbreak iPhone 4 and install the app on your iPhone  by searching for ‘MiTime’ in Cydia. Add http://cydia.pushfix.info/ as a source in Cydia and search again if you are unable to find it.
2. Run MiTime and if your phone number matches the number you gave on the website, you will be authorized.
3. If the next screen says ‘Ready for activation’ then go ahead by hitting the ‘Activate my FT’ button. When asked ‘Do you wish to use a credit to activate FT now?’, press ‘OK’ button. You will then see ‘An activation request has been generated’ message for a moment before seeing the final ‘Activated’ screen.
Only send one activation request and wait for up to 15 minutes. It should only take 1 minute, but don’t waste your activation credits. If it doesn’t activate after 15 minutes, eject and re-insert your SIM. Wait 1 minute and then reboot.
Once it shows Activated, it has saved your token and FaceTime is fully enabled.
4. For those of you who are unable to view the ‘Ready for activation’ screen in step 3, wait for a while till MiTime resets FaceTime and re-springs (takes around 2 minutes). Then unlock your iPhone and within a minute you should see a warning about the cost. Click OK and you should see the ‘Activated’ screen.
If it says “Activated” you can stop here. It will back up your FaceTime activation for later recovery.
After installation,

A) If you turn off FaceTime or it gets turned off somehow, don’t turn it on in Settings -> Phone. Run the MiTime app and it will fix it and turn it back on.
B) If you ever see the warning message about costs again, tap Cancel and run MiTime to see what is going on.