Does anyone know if I can change seats for a higher class for free during Check In with Basic Economy? I'll be travelling HRL to LHR soon. I already purchased economy seats so I will not be waiting to pick up available seats at the 24-hour mark.

With Economy, back in January, I was able to swap from Economy to Premium Economy for free. No status, but I'm a United credit card holder with boarding group 2 and 2 free checked bags.