Following online instructions, you can use a fake, all-zero phone number to make a "No Caller ID" call. If you put this number on your "do not call" list, real people who haven't given you their number won't call you. This is an important step to block no caller id calls on iPhone There's no way around it: this doesn't work. Most calls from people who don't have caller ID will still be answered with this method. Use the tips above to stop calls that don't show who is calling.