To block someone from calling your cell phone, you first should contact your phone carrier. Your carrier may or may not have the ability to block numbers. If your cell phone will allow you to block numbers, you may be able to do this by adding the phone number into your contact list. Next, follow these steps: add the number into the group setting from your menu screen, go into the settings option and select security, enter your phone's lock code, select the option to block and choose the contact option. If your phone will not allow you to do this, you can try assigning a silent ring to the number you want to block.