They did refund it, but they said it was a "one time exception". When I questioned it further, they said that because there were two passengers being booked, and my travelling companion was only silver, that's why the charged it.

I understood as long as family members were in the SAME PNR as the GM that the direct ticketing charge did not apply. Apparently not? I gave up arguing about it - too exhausted for another Delta battle today.