Messages

go to Settings > [your name] > iCloud and check the switch position for Messages

If the switch is ON, then you cannot recover your deleted messages and your messages would not be contained in an iPhone backup (no need to read any further)

If the switch is OFF, then you might be able to recover your messages IF you have an iPhone backup that contains the messages you are trying to recover. In which case you'd need to restore your iPhone to that backup. In doing so, you'd likely lose some data between now and whenever your backup occurred.

Locate backups of your iPhone, iPad, and iPod touch - Apple Support

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

SS_0122 Said:

"Messages : How can I retrieve accidentally deleted text messages?"

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Recovering Deleted Messages:

What to Consider:

A. Restore from Today's Backup:

Restore your iPhone from a backup of it that contains these messages, and you could recover them.

B. Check Messages App:

If messages was enabled on your iPhone along with your Apple computer, then check and see if the Messages app is enabled on your Mac to see if it exists in it. You'd start up your Mac, not connecting to the Internet, and open the Massages app. Then proceed from there with retrieving it. Important: Be certain you do not connect to the Internet while booting up, as syncing would delete it. So, power off your router to avoid the connection.

Elsewise, if they're gone, they're gone. That's just the way it is :(