How to recover deleted text messages

If you're using iCloud Syncing for Messages, once you delete a message, it's gone for good.

Keep all your messages in iCloud - Apple Support

If you're not using iCloud syncing and you have a back up containing the messages, you can restore your phone from that back up.

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

Note that restoring your phone from a back up will overwrite everything currently on it.