One of my client have iPhone 4 which have iPhone iOS 5.1.1 forgot pass code, and he want not to delete all call history and other data. I have found a simple solution on internet to bypass this code with a simple trick. This is a video trick found on Dailymotion video. With first try i have success to remove the code, and all data and call history same as before forgot pass code. Below in video you can find the way to remove pass code without losing data.
iPhone iOS 5.1.1 Pass Code Bypass Trick
Try this trick on your own risk, we are not responsible any lose. You can use this method for all iPhone smartphones and iPod having iOS 5.1.1 like iPhone 3g, 3gs. 4g, 4gs etc.