Dialing *67 directly before dialing a phone number deactivates caller identification, or caller ID, and the caller ID of the person you are calling will read "private number" instead of displaying your phone number. Dialing *67 before a phone number temporarily blocks caller ID when calling businesses and individuals, but it does not work for calls to toll-free numbers and emergency services.
If you have an iPhone or an Android device, you can also block your number from displaying on caller ID in the settings of your phone. On your iPhone, select Phone in the Settings menu, then select Show My Caller ID. From there you can choose to either show or hide your number on caller ID. This iPhone feature is available with all carriers excluding Verizon Wireless.
If you have an Android device, first open the Menu, then select Settings. From there, select Call Settings, then Additional Settings. Select the Caller ID option. From here you will be able to either hide your number, show your number, or restore this setting to the network default, which will revert back to showing your number on caller ID.
Cellphone carriers can also permanently block caller ID if customers request this service. Carriers' customer service numbers vary, but dialing 611 typically works for those in the United States and Canada. Although permanent caller ID blocking is irreversible, dialing *82 before a phone number temporarily reactivates caller ID.