Messages lost

Message once deleted is gone for ever. If you have iTunes backup you may try restoring from it.

If you have deleted a text message that you had received from one of your contacts and want to retrieve it now.

You can't do it, normally. The only way is to restore from backup

1. The way to restore messages via an iCloud backup is to completely erase your iPhone and try restoring it from an iCloud backup, as so long as you have one such backup; before the text messages were deleted.
   1. Check in Settings > [Your Name] > iCloud > Manage Storage > Backups.
   2. 
   3. If you do, then you need to factory reset your iPhone before restoring it via that iCloud backup. Note that the last successful iCloud backup time/date is available beneath the Back Up Now button.
   4. Do not forget to take fresh backup on iCloud before you start the above process. You may need to restore from this fresh backup later.
2. If iCloud didn't work, there is another option to try. First you can try recovering deleted text messages via an iTunes backup.
3. Unless you disabled the automatic sync option in iTunes, you should have created a backup every time you synced with your PC or Mac.
   1. Connect your iPhone to the PC with which you sync it. iTunes should open (if not, open it manually)
   2. You should see your iPhone appear. Select it
4. Now choose 'Restore backup'
5. 
6. All the data you previously backed up will now replace the data on your phone. It will take a few minutes. As long as you haven't backed up subsequent to deleting those messages, they should now appear on your phone
7. Do not forget to take fresh backup on iTunes before you begin the above process. You may need to restore from this fresh backup later.

What does iCloud back up? - Apple Support

https://support.apple.com/en-in/HT207428

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

https://support.apple.com/en-in/HT204184