Why does my iPhone call log show a lot of "No Caller ID"?

[slapple]

I recently upgraded from iOS 6 to iOS 8, and I noticed my iPhone recent calls has a lot of "No Caller ID" in it. It used to always show the phone number or the contact's name, but now a lot of those have been replaced with "No Caller ID". What does that mean, and how can I have it show the phone number/contact name again?

 

[I7guy]

I recently upgraded from iOS 6 to iOS 8, and I noticed my iPhone recent calls has a lot of "No Caller ID" in it. It used to always show the phone number or the contact's name, but now a lot of those have been replaced with "No Caller ID". What does that mean, and how can I have it show the phone number/contact name again?

When a known phone number calls do you see the number?

 

[slapple]

When a known phone number calls do you see the number?

On the few calls that I've received so far, yes.

I guess if this is only a problem with the call log, then it's not a problem, since the log will eventually delete old entries.