Blocking a Number From iPhone and Android Devices
To block a phone number on an iPhone, the number must first be added to your Contacts. Once added to your Contacts, go to Settings > Phone > Blocked > Add New.
The Add New option will open your Contacts. Click an entry from your Contacts to add to your Blocked List. After doing so, you won't receive phone calls, messages or FaceTime requests from the blocked number.
To unblock a number from your Blocked List, swipe it to the left until you see the "Unblock" option.
To block a number on an Android device, choose Phone > More > Settings > Call Blocking > Block List.
From the Block List page, you can block a number several ways: 1) enter the phone number and press the + sign, 2) tap Log and choose a number from your call log, or 3) tap Contacts and choose a number from your contacts.
Once a number is added to your blocked list, you can unblock it by tapping the minus sign next to the blocked number.