How to retrieve erased text messages

If you have a backup made before you deleted them, you can restore them from that backup:

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

keeping in mind that the restore operation will overwrite all the current data on your iphone. Restore and backup is: all or nothing (you can't restore your messages only).

If you don't have a backup, the deleted messages are gone, sorry.

You can only ask your correspondent to send them back again to your device.

Regards

Giulio

The only way to restore deleted info is to restore from your most recent backup.