Re: FaceTime issue
Does the person you are calling also have an Apple device with FaceTime installed.
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If they do: See if your iPhone can be updated to iOS 16.6 : About iOS 16 Updates - Apple Support
else: if you already have iOS 16.6 installed:
Try re-starting your iPhone again (deletes temporary files / re-establshes the connection)
How to: Restart your iPhone - Apple Support
Then check again you have the person's correct contact details listed in your Contacts app and try again.
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If they don't have an Apple device: You will need to set up a link and send it to the person to use FaceTime:
How to: Create a link to a FaceTime call on iPhone - Apple Support
The person will then be able to: Join a FaceTime call from an Android or Windows device - Apple Support