I recently was booked for a Tango fare, and was furious that you get no miles at all (I'm only Prestige). When I asked if I could pay the difference between Tango and Tango+ and then get the miles - no problem. So I did that. It wasn't much money for the miles. It was a one way fare, as my return date was uncertain, so when my employer booked the return fare, Tango again, I immediately called and changed it to Tango+. The only charge was the difference in the fare.