I've booked plenty of UA awards, but never burned a mile on DL... Say I've got a low-level business award booked, and one segment had no business award space open, but was available in economy - so I book an award with mixed cabins. Mileage was deducted at the business price obviously. If business award space opens up on that economy segment, can I call in and have it changed from economy to business without triggering the $150 change fee? Is it a YMMV situation? Thanks!