Unable to make phone calls on my iPhone 11

See what to do here:

If your call fails or you can’t receive calls on your iPhone - Apple Support

Tammy ~ Your iPhone 11 is several years old and so worth checking for a weak, aging battery which may not be able to supply sufficient power to the iPhone's antenna for connecting with cell tower signals. So...

Does your iPhone 11 still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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