Hello friends! I mistakenly booked a longer layover in LHR than I wanted (6.5 hours rather than 2 hours) before my final destination of IAD this Christmas season. My fares are K economy on LH and I don't have status on LH or UA.

My parents would love to know when I might be home for Christmas

UA operates both of these flights to IAD. Disregarding how nice London may be (!), can I make a same-day change to the earlier flight if K fares are still available on it? For $75, the UA same-day change fee, right? Any other budget-friendly course to recommend to be home sooner?