Recovering permanently deleted Messages
How do I recover my permanently deleted messages
[Re-Titled by Moderator]
Question marked as
Just to confirm, by permanently deleted, do you mean they are also gone from your "Recently Deleted" folder? If so, it unfortunately means the messages will likely be gone from good.
The only other solution which could work would be restoring your device to an older backup. You would have to consider if this is worth it due to the loss of data (through restoring from an older backup), and this would only work if the iMessage in question is saved in that backup.
Recover deleted text messages on your iPhone or iPad – Apple Support (UK)