If your are the android user, you can get them back with a data recovery. Actually, there are only 3 steps for you to recover. Step 1. Run this program and connect your android device to the computer Step 2. Analyze and scan your android device for lost contacts Step 3. Preview and recover lost contacts from android devices Go and read more details from: http://goo.gl/G5JYn2.
6 months ago
Last edited at 1:49AM on 9/29/2013
If you backed your phone up before you did the update, just restore the backup. If you have just your contacts saved in your address book then plug your phone in, go into contacts on iTunes and sync contacts. If you don't have either then you have to manually enter them back in
To get your contacts back on your phone after updating it depends with your phone model. If you have Android, then you can retrieve the backup from G-mail account if you had synced them. If it is an OS device, then you can get the contacts from iTunes.