Yes, have already done this, a little over a week ago. I understand they have a lot of DOT complaints to deal with and may be backlogged. Delta has acknowledged receiving the DOT complaint but yet to respond.

Was also considering a BBB complaint, but wanted to know what the general consensus is - should they be obligated to refund the cash portion in cash or not? After the fact we can see that they claim that miles plus cash tickets are AWARD tickets, and the $180 was immediately converted to 10,000 miles. But at the time of purchase this was not clearly stated. Had no idea all that this was actually purchasing 10,000 miles for a mileage ticket. (Have done that before, and it was a separate transaction, first buy more miles, then book an award ticket). Miles plus cash is a very misleading name. Should have called it "Buy more miles" or something.

The rotten thing is that his dad's FF account had enough miles to cover the original ticket in miles only. Never would have booked miles plus cash if it were clear that it was actually just a purchase of miles... $180 for 10,000 miles didn't seem like a good deal.