Try Coolmuster iPhone Backup Extractor, you can use it to extractor contacts, messages and other kind of files from iTunes backup.
Q: "The upgrade process was failed when I was trying to update my iPhone 6 Plus to iOS 8.1 early this morning. I can restore some content stored on iCloud backup, such as contacts and notes, but I couldn't get back my text messages, which are important for me. How to recover my lost messages? Can any recovery app do the job for me?"
Besides iOS update, text messages can get lost owning to:
1. Wrong operation, e.g. mistaken deletion of text messages;
2. iPhone Jailbreak;
3. iPhone factory settings restore;
4. iPhone has been lost or stolen;
5. iPhone was damaged, broken.
No matter you have created backups of your iPhone or not, here in this guide you will get three ways to retrieve the deleted messages from iPhone 6/5C/5S/5/4S/4 with the help of an iPhone data recovery tool - PhoneRescue.
Resource from:3 Ways to Retrieve Deleted Text Messages from iPhone 6 (Plus)
When files are "deleted" they are not actually removed from your iPhone, until something else overwrites them. So by saving anything else to them you may have overwritten them. There is a decent chance that you can restore them though. I've successfully used undeleted plus before to restore messages that were accidentally deleted on my iPhone. You can have a try of the iPhone SMS Recovery software, and you can go through the tutorial of it if you'd like.
Last edited by Kolpoiu; 06-05-2015 at 08:59 AM.