I've booked IND-IAD-MUC in LH J (88k miles I class) with IND-IAD in XN. There is now IAD-MUC in F available but the IND-IAD is no longer available in XN class. Will I be able to upgrade to LH F by paying the mileage difference while maintaining the current reservation or will an "upgrade" to LH F not be available if IND-IAD is no longer available?