Currently Being ModeratedFeb 9, 2013 3:12 PM (in response to Sunshine28)
I believe the way Caller ID works on the iPhone is that it will check your contacts for the number calling and then display their contact details. Therefore, you need to make sure you have accurate details for everyone that may call you. If the caller does not want their Caller ID shown, your iPhone will show number as Blocked.
If it's your Caller ID you want to hide or show, to to Settings > Phone > Show My Caller ID > Slide to On