Troubleshooting Lost Messages:
A. Log in to your Carrier's Site:
Logging in to my Carrier's site, I can see my messages going back 90 days. So, see if you can do the same.
B. Restore from Today's Backup:
Restore your iPhone from a backup of it that contains these messages, and you could recover them.
C. It's Time to Upgrade to a Newer iPhone:
Expect your iPhone to be ten generations old soon. Apple has a tendency to provide updates for 7 years after a device is released, and then stops providing them. So, your device is quite vulnerable to issues, because bug fixes are no longer provided by Apple for your device.