Originally Posted by
sbm12
You don't have to go this route. You just don't request the upgrade right away and process the purchase normally. Then you go back in and get the Y/B/M-Up after the email has been sent.
Even if they only show the booking code on the receipt it would likely show CU or AN (or whatever we're calling them this week). And those are not coach buckets.
This is the way I did it. Once I had made the reservation, I didn't upgrade it. I printed out the receipt. I then called OP and the lady happily upgraded me. Now I have my receipt for the M fare and the upgraded reservation.