Yesterday I booked a trip to Sydney in Club, flying back to LHR at January 19th with Qantas. Today I realized that within 3 weeks I'll receive my Gold upgrade for two. I called ba reservations to change my flight to a BA flight (so I can use my upgrade). They told me that I booked D class and there is no British Airways D class availability between January 15th and January 20th. When I check airtravel.tk there's enough D class availability on BA flights (e.g. BA 10 or 16).
Any ideas what to do (exept paying 1500 euro PP for a upgrade to a flexible Club ticket!)? Who's telling the truth?