There is most likely a problem with the software in the phone, if it persists, let your phone company know.
hold the "home" button and the "lock" button at the same time and release it.
press the middle button and the lock button at the same time :)
Press and hold the lock button
You click the same button used to turn the phone off/on
on the right side, you will see a button with a design of a lock. press that button
Hold the lock button for 5 seconds.
You usually do Lock Button + Home button for Samsung devices making sure you click the lock button first or you'll end up at the home screen :)
I don't know and why is this listed in iPhone?
You can purchase network lock control key for Samsung galaxy ace from Classicunlocking.com .. And you can have a look up at this free guide called Mobileunlockguide.com … where you can find instruction how to unlock your phone step by step...
Press the lock button on the side and hold it
On the right hand side of the phone on the side, there is a camera and lock button. Press the top one, with the picture of the padlock on to lock it.
unlock it by holding down the lock button on the side