I am getting very conflicting information from both various departments at United and some very savy FTer's.

Hypothetical question:

I purchase a fully refundable ticket C class ticket LAX-AMS. Cost $6000. I charge the ticket to my MP Visa. I decide later to buy a full fare refundable F ticket from LAX-LHR. Cost 10,000. I make a new reservation and apply the cost of the first ticket to the new reservation (exchange it like a voucher) and charge the additional $4000 add collect to my American Express.

Now I decide I want to refund the whole new LAX-LHR ticket. Where will the refund go? All $10,000 back to Amex? Or does the system track the original card depite the new ticket number and all and split it back $6000 to Visa and $4000 to Amex?

I hope that made some sense....