How Can I retrieve deleted texts on my iPhone 11?
How can I retrieve a deleted text conversation?
iPhone 11, iOS 14
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If you were using Messages in iCloud, then I am afraid they are gone for good.
Use Messages in iCloud - Apple Support
Otherwise, you will have to restore the iPhone from a backup that has those messages:
Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Be aware that restore is an all or nothing process. You cannot only restore text messages (for example) and any information between now and when the backup was created will be lost when you restore.