I'm in the middle of a JFK-LHR trip and need to change the date of my return to the following day. I'm PM and a MM but not sure if that's relevant. I paid $848.75 for the r/t (premium select on Virgin Atlantic for the overnight outbound, main cabin Delta on the daytime return with free PM upgrade to C+). If I try to change my return flight home (same flight next day), it says it says original flight value is $848.75 - $300 for the change fee. Return cost is the same so my out of pocket is $300.

If I cancel the remainder of my ticket, any idea how much I would get back? A new r/t ticket starting with LHR-JFK (main cabin with free C+ upgrade) and returning to LHR on a random date 2 weeks later (basic economy because I'm not going to use this anyway) is $498 USD (approx after conversion). Wondering if canceling the return and booking a new r/t might be a more cost efficient way to do this. I'm not sure how far I can go through the cancellation process to see the ecredit before I can back out.

For reference, booking a new one-way LHR-JFK is $1,840 - more than 3 times the price of a r/t!

Thanks in advance.