When you delete a message on your device, it may not be fully removed from your device's memory as well as from your chat history. However, you can still permanently delete a deleted message from your chat history by following a few simple steps.
For iOS devices running iOS 14 or later, you can delete a deleted message from your chat history by following these steps:
1. Open the Messages app and select the conversation from which you want to delete a deleted message.
2. Swipe left on the message you want to delete, or select and hold the message until the options menu appears.
3. Tap the "More" option, represented by three dots icon.
4. Select the check boxes next to the messages you want to permanently delete.
5. Tap the trash can icon in the lower-left corner of the screen.
6. Confirm that you want to delete the selected messages permanently.
This will delete the deleted messages from the chat history on your device and ensure that they cannot be recovered. It is important to note that this process only applies to messages stored on your device. If the messages were backed up to a cloud service, they may still be accessible from there.