My phone is giving me a message saying that my phone has got to be updated to receive or make calls

Where and when is this message being displayed? Can you post an image here, please?

One thing that could interfere with calls is the carrier settings. Take a look at this article from Apple to see if it helps somehow Update your carrier settings on your iPhone or iPad - Apple Support even though I never saw it prevent users from making calls.

Some more from Apple Support If you can't make or receive calls on your iPhone - Apple Support that basically comes down to the carrier settings or iOS (that you're already running the latest).