Q: How can I retrive text messages I accidentally deleted?

If they were on your device when you last backed up, restoring the backup should recover them.   (The backup includes text messages.)

If it's an iCloud backup, you restore it as explained here: https://support.apple.com/kb/ph12521.

Have you ever used iTunes? If you have backed up your data through iTunes, when you click "Restore" button in iTunes, It will detected the backup files automatically. Select the backup file and you can restore the data. But you must have backed up data before, and include text messages.

Or you can via iCloud to recover your deleted text messages. Have you ever backed up data via iCloud? It is similar to iTunes. And if you have not backed up any data, iTunes and iCloud can not work.

So, you can try other method to recover the deleted text messages. some apps maybe help you get back the deleted text messages.