There is a known issue with the incoming caller ID not showing however if its only your contacts and other calls are showing it might be something else. I would be having a word with support and you can do that via the live chat link below if you wish.
Many thanks, Yeldarb. The problem is still unresolved. It has to do with all my incoming international calls from my contacts and others. It's always "No caller ID" or "Uknown". This is very frustrating. I understand the matter has been reported to Apple and I was given an incident number. Apple is yet to get in touch. So I continue to suffer the frustration while I am faithfully meeting my monthly obligation on the phone an plan to Optus. This is mind boggling!
Again, I am grateful.