My phone fails to update and now I cannot make calls.. help!

Go through the various suggestions in the support article below particularly looking for carrier update, but if they don't help, and your network carrier can't help, then contact Apple Support for further investigation.

Support article: If you see No Service or Searching on your iPhone or iPad - Apple Support

My phone fails to update

Have you follow -> Related Article -> If you see an Update Failed or Apple Pay Not Available alert after iOS update or restart

now I cannot make calls

See this Apple article: If you can't make or receive calls on your iPhone

If you can't make or receive calls on your iPhone - Apple Support