If you have received calls on your cell phone that are identified by the device's caller ID as "Unavailable" or "Restricted," several issues can be at play. These caller ID designations are the products of settings on the caller's end or network restrictions and have nothing to do with your phone's settings.
Cell phone calls designated as "Unavailable" on a phone's caller ID are placed from an area or region from which your wireless service provider or phone company is unable to retrieve a phone number. These types of calls can be placed from other parts of the world, using calling cards or from numbers that have to place calls with the assistance of a switchboard operator, such as a college or hospital. A "Restricted" phone call comes from a caller who has specifically blocked your phone from identifying his number.
A caller who blocks his number from appearing on your cell phone's caller ID activates this feature by pressing "*67" on the keypad before dialing your number. This feature typically generates a "Restricted" identification on the receiver's end, but it can also be identified as "Unknown" or "Unknown Caller." Phone calls that show up as "Unavailable" are the result of your phone carrier's inability to identify a caller's number.
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Although any caller can block your phone from identifying his phone number, thus producing a "Restricted" designation, most people who use this feature do so because of an organization's sensitive nature. For example, government officials often use this feature to protect their organization's privacy and to prevent random callers from having access to high-ranking officials. Calls that produce an "Unavailable" identification can be from out-of-country marketing companies or placed by foreign mobile phone users who are calling you from outside their normal coverage areas.
Some wireless service providers give you the option of disallowing "Restricted" and "Unavailable" caller ID designations if your situation involves a matter of personal safety, such as harassing or threatening calls. However, because the "Unavailable" identification is typically out of the provider's control, the lifting of this feature is limited. The "Restricted" disallowance is limited to nongovernmental callers only. If you have these restrictions lifted and the calls are coming from an organization such as a college or hospital, only the organization's main phone number appears, not the extension from which the call was placed.