is there not a way to block a number unless they contact you first?

Block Calls From a Number:

1. Tap the "Phone" tile while on the Start screen
2. If necessary swipe left or right to view the "history" screen
3. Tap and hold the phone number you want to block
4. Tap "block number…" > "OK"

Block Messages from a Number:

1. Swipe left while viewing the Start screen
2. Scroll to and tap "Messaging"
3. Tap and hold the phone number you want to block messages from
4. Tap "block number…" and press "OK"

Unblock Numbers for Calls and Messages:

1. Swipe left from the Start screen
2. Scroll down to, and tap "Settings"
3. Tap "call + SMS filter"
4. Tap "Blocked numbers" and then tap and hold the number you want to unblock
5. Tap "Unblock"

Forward All Calls (Unconditional Forwarding):

1. Tap the "Phone" tile while viewing the Start screen
2. Tap the "more" icon (…) located in the lower-right area of the screen
3. Tap "Settings" and enable the "Call forwarding" switch
4. Enter the phone number to forward calls to
5. Tap "Save"

Cancel Call Forwarding:

1. Tap the "Phone" tile
2. Tap "…" and go to "Settings"
3. Swipe to, and tap the "Call forwarding" switch to turn the feature off

View and Reset the Call Log:

1. On the Start screen tap the "Phone" tile
2. Swipe to the "history" screen and tap a call log entry to view more details
3. To reset the call log, go to the "history" screen and tap "…"
4. Tap "select calls" and mark the check boxes associated with the call log entries you want to delete
5. Tap "Delete" twice to confirm