Good afternoon rgnapp111,
Welcome to the Apple Support Communities!
We'd like to help with the issue you are having with the SIM card on your iPhone 13 Pro. Since we don't know what thread you are referring to, can you provide a little more detail as to the troubleshooting you have already done for this issue?
Your profile shows iOS 15. If you have not done so already, please make sure your iPhone is backed up either to iCloud or your computer. Then update to iOS 16.1.
Update your iPhone or iPad
Next, make sure the cellular provider settings are updated as well. You may need to get a new SIM card from your carrier to address this issue.
The resources below should help with this:
Manually update your carrier settings on your iPhone or iPad
When a carrier settings update is available, you'll be prompted to install it. Installation takes less than one minute, and you can keep using your device normally. If your carrier releases a mandatory update, you'll see an OK button instead of an Update button to let you know that the update was downloaded and installed.
If you dismiss the installation notification, you can manually update carrier settings by following these steps:
1. Make sure that your device is connected to Wi-Fi or a cellular network.
2. Tap Settings > General > About.
3. Follow the onscreen instructions to install your carrier update.
If you insert a new SIM card into your iPhone or iPad, you need to download the carrier settings for your new carrier.
To see the version of carrier settings on your device, tap Settings > General > About and look next to Carrier. To see additional carrier information, tap the version number. To verify that you have the latest carrier settings installed, contact your carrier.
Remove or switch the SIM card in your iPhone
Let us know if the issue persists after performing these troubleshooting steps.
Take care.