Usually when privacy is the concern, there are ways you can use to call anyone anonymously by using available apps for iDevices, Android or PCs. You can even use your smart phone settings to hide your phone number depending on your device in some cases. Almost all smart phones have feature of ‘Block Caller ID’. If you change your phone settings to block caller ID, the receiver phone will display as Unknown Number or Anonymous Call while you call them. This is a secure way to deal with an unknown person or calling back to non-familiar number. But this method will set the device to permanently mask your phone number while you make calls. You can use apps or use tweaks to still call anonymously without changing your smart phone settings.