From Google Voice, you can block a phone number from ringing on your cellphone with call rules designed to help you filter your incoming calls.

The iPhone doesn't actually provide a way to block phone numbers. You can tap "Decline" when the phone rings, but you can't just tap a "Block" button to keep someone from calling anymore.

Dial that code before the phone number, and it will temporarily deactivate caller ID. On the receiving end, caller ID will usually display “private number” because it has been blocked.

Block phone number on iPhone Blocking a phone number on an iPhone can be a useful feature if you want to avoid unwanted calls, messages, or FaceTime requests from specific contacts.