Accessing deleted texts
How can I access deleted text messages from two months ago?
iPhone 7 Plus, iOS 12
The only way you can recover past texts is from a backup that you may have created on your computer or on iCloud. Note that your messages recovered from the back up will only be as current as the day and time that you created the backup. If you do not have a backup then you will have lost your deleted messages.
Here is how to restore your iPhone from a backup Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Good Luck.
Axel F.