Seems an ok add-on to me.
"Select up to ten numbers and save 10% every time you call them, with 20% off your BestFriend number. What's more, with Friends & Family Overseas, you can add an extra five International numbers."
Just give your account number and numbers for the savings and you're away.
If you call one person a lot seems a good deal.
As nono said, do the automatic one and just add the "best-friend" one.
Hope this helps someone.