Originally Posted by
eternaltransit
You can't ever get a refund moving to a lower priced RBD so the question I think is moot

The website breaks down the changes into fare differences, taxes and change fee so if there is no difference in fare you know you are in the same fate bucket.
Oh, oh know that, I just remember reading here sometime ago, that when someone made a change to a flight where a lower RBD was available, he was automatically rebooked into that which had lower mileage earning and different change rules.
I have booked a more expensive for as I needed the miles, but am worried that using MMB will rebook me into the lowest available fare (which in my case I know there is a cheaper Saver fare available).