Hi, Cosmik_723, and thanks for reaching out. We see you're having issues with an alert about a potential SMS charge relating to iCloud activation. We'll be glad to help.
By any chance, are you using Messages in iCloud? You can check by tapping Settings > [your name] > iCloud, and looking to see if Messages is on. Also, to verify, are you able to send and receive both SMS and iMessages?
From your post, it sounds like this message is popping up frequently. Does it happen after you restart your device, when you switch between Wi-Fi and cellular, when you use a particular app, or does it seem to happen only when cellular service is interrupted?
If you tap Settings > General > About, do you see any prompts to update your carrier settings? Which iOS version are you using on that screen?
We hope this helps you.
Take care.