Does official AT&T unlock also upgrade the operating system? I have an AT&amp;T iPhone 4 running iOS version 5.1.1. My contract with AT&amp;T is complete, and they have authorized my unlock. However, the process is to backup and restore from iTunes, according to the instructions they sent.

It seems like an obvious question, but I couldn't find the answer searching. Does going through that process upgrade the operating system? I do not want to upgrade the OS because I am concerned it will make the phone slow.

UPDATE:  I followed the instructions from M K, with the results described EXCEPT no iTunes unlock message.  

However, even though I had received an immediate response on the AT&amp;T portal with instructions how to unlock, 24 hours later I received an email from AT&amp;T, containing the same instructions as the portal, but now asking me to wait 24 hours after receipt of the email.  So I will wait and try again tomorrow.

UPDATE #2: I followed the instructions from M.K. again on the following day, 48 hours after I had submitted my request, with the results described EXCEPT that when I reconnected the phone, iTunes gave me a spinning beach ball, and then crashed.  Then I got a message box telling me that iTunes quit unexpectedly.  I took the "restart" option.  iTunes came up, processed for about 20 seconds, and then gave me the message that my iPhone had been unlocked, in the main iTunes window.  No OS update (still version 5.1.1)  Thanks!



UPDATE #3: The unlocked phone is, in fact, unlocked -- I took it to Sri Lanka and the Maldives.  In each country, I was able to buy a cheap GSM card, only about $3 in Sri Lanka, which let me surf the Internet and make and receive local calls for the week I was there.  And I am still running iOS version 5.1.1
Yes, a backup and restore will force iTunes to update the device with the latest version of iOS. In order to get around it, follow a slightly different procedure described at How to restore iOS without updating (edited instructions here):


  
  Backup the iPhone in iTunes
  Disconnect the iPhone from the computer
  On the iPhone, go to Settings > General > Reset and select "Erase All Contents and Settings"
  Wait for the phone to display the swipe to setup screen
  With iTunes already running, connect it to the computer 
  iTunes will display the unlock message
  Click on Done
  iTunes will present the option to restore from a backup
  Restore from the recent backup you made
  iTunes will also sync all your apps after the data and settings restore is completed (the entire process may take a while depending on the amount of space used on the iPhone)
  


See: