Some people have reported that in order to get no change / cancellation fees, you have to pay for the entire flight with the VX CC, and if you use any travel bank funds, there will be change/cancellation fees. This essentially means that you can only cancel/rebook a flight once without paying fees.
This is
not my experience.
I had a non-refundabe F fare for around thanksgiving ($424). Paid with the CC. When they had their 20% off promo I cancelled and rebooked for the discount, and used the travel bank to pay. I just got the email about the 50% off promo, so I did the same thing. The fare had dropped, so I got 50% off the new fare (I paid $157). I was not charged a fee to cancel the 2nd time, even though the flight had been paid for with travel bank. The fare was non-refundable, and was well beyond the 24-hour window.
Just a data point, and YMMV, but I certainly didn't get charged. I didn't do anything special -- I just cancelled online and there was no fee charged; the whole amount got credited to my travel bank. I wasn't 100% sure it would work so I even took a screenshot of the page (which showed no fee) before I confirmed the cancellation, so I'd have some ammo to complain if they did charge the fee
