There may be times when you do not want the person you are calling to see your phone number. Reasons why you may want to conceive your cell number include:
o You do not want the person you are calling to see that you've called them 10 times in a row.
o You do not know the person you are calling and do not want them to have access to your number.
o You are calling a business or an unknown number and do not want them to know your number.
If you decide that you would like to keep your cell phone number a secret, you will need to block your number. Blocking your number can be done temporarily or permanently. Temporarily blocking your number on a call by call basis is a good idea if there are only a few people who you wish to hide your number from. To temporarily block your number so it is not displayed on the recipients caller ID simply dial * 67 before dialing the number (IE * 67 111-111-1111).
Keep in mind, you should know that when you use * 67 to temporarily block your number there will be nothing to inform you that your number has been successfully blocked. Therefore, if you want to make sure it works, do a quick check and call your home number first before you attempt to use this service on someone else.
If you really want your cell number to be private, and wish to block your mobile phone number permanently, you will need to contact your wireless provider and request a "line block". Once the line block has been established, your number will not appear to anyone. However, if, for some reason, you would like your phone number to be displayed for the recipient, you can reveal your phone number by dialing * 82 before dialing their phone number.
Finally, you need to know is that your cell phone number will not be blocked from any toll free numbers (IE 800 numbers), or from emergency services.
In addition, blocking your cell phone number may be a good idea if you are trying to find out who owns a phone number by calling the mystery number back.
Source by Steve Cowen