There is probably not much you can do, the seats were shuffled, probably because the aircraft was changed from a 77W to an A351. Though row 45 has the same number of seats, you'd kind of expect them to keep the assignments.

In the end, seat assignments are not guaranteed and changes do happen. At least 45J will still keep you reasonably undisturbed as the legroom is the same. If you have an expertflyer account, you should set alerts for 45A and 45K. Maybe you get lucky and they have requested a mileage upgrade? Or they rebook.