I have a RT booked to LHR from the US as an award ticket on Delta - outbound in Upper Class, return in coach.

I have found Upper Class award availability for the flight back to the US, and would like to change my return flight to that date. However, Delta reservations says that they do not see that availability.

I then booked the seat as a one-way award from LHR on the date I wanted, and called Delta to see if they could somehow merge the records to give me the flight I booked for the return combined with my existing outbound reservation. They could not do that.

Any suggestions (I can't change it online, and keeping the one-way reservation back from LHR does not work because of the Europe originating surcharge.)