iCloud
I can’t log into iCloud as well as use my iPhone to call and the update issues also
iPhone 6
Is your iPhone updated to the latest software? I do know that this could be a long shot but some older software had been stopped from connecting to network serviced due to a security issue that was fixed by a later release of iOS. I would recommend updating your iPhone to see If that fixes it. Also, was your phone able to do these things before now?