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I found this information on the internet >>>First point to note is that this is nothing to do with handset settings on functionality. There is no switch on or off for caller ID for incoming calls on iphone -- the caller ID setting in your phone setting is only for whether you want to show your number to people you call. I spoke to the help desk at apple, they walked me through this and said there is really nothing you can do on the iphone that could solve this and recommended I not try a system restore as that would just be a headache for me getting everything back how I wanted it. Its a carrier issue - no question.
I phoned my carrier and spoke to the mobile tech support people. They said the caller ID service was not showing on the account. They said it is usually there and they could try a few things to get it back, with the last resort being to escalate the query to another level of tech support. The guy then proceeded to try a simple "refresh", of the account services. That didn't work and then he found that someone had put a code on the account to block caller ID (go figure??) so he deleted that and refreshed and then called my iPhone from another line to confirm it was working. So I had the service working correctly before I hung up from my landline.          Source: Mac Rumors.