Sign up for TrapCall (google it). You can sign up for the cheapest plan which is below $5 a month. Sign up it for like a month then cancel after. Trapcall reveals the restricted number. You should see the phone number.
You can add usage controls to your account. This feature will allow you to block restricted numbers also. The feature is 4.99 a month. I have provided a link for more information. Click here http://search.vzw.com/?do=viewdoc&id=20989 Hope this helps!