Today I faced a strange issue with my Apple iPhone 4S after upgrading from iOS5.0.1 to iOS5.1. All the data from your iPhone is first backed up automatically and then restored when you upgrade iOS. So during this transition my contact list got weird and the sorting order changed from Last Name, First Name to First Name, Last Name. I tried setting the order back to Last Name, First Name but it reverts back automatically. Finally I found the solution to fix iPhone contact list sorting order.