How can I block my phone number display to viewers?

Before you dial a number press *67. This definitely works on most landlines as well as cell phone providers. If you want to keep a check if it worked when you press *67 on landline, then you should hear three brief tones. You then continue to dial the rest of the number, on the other persons caller id. It will display blocked call. On a cell phone you will not hear the tones so try it by dialling *67 and calling yourself on your landline if you have caller id. Beware, people will come to know that you deliberately blocked your number because when you use *67 on the caller id it will say blocked call. And if you had your number private or unlisted then it would show up as a private number or restricted caller. Hope this helps you.