Stopping fb messenger accessing my phone app

How can I remove permission for messenger to access my phone app on my iPhone 11? I have turned the option off on the facebook desktop site as recommended by fb. I have a page for a brand and I am receiving messenger calls through my phone that actually show up in my call log at all hours of the night. I find it hard to believe Apple hasn’t given us a way to stop this on the phone, I checked privacy settings, the individual app settings for both, and I can not find a way to revoke permission to access my phone app or my messages app. I would have expected to find both in the privacy settings, similar to photos, yet they are not their. I recall this being available on older iPhones. Please help!