Hello,
I'm an AAdvantage flyer, currently no status, who flies often on Alaska Air with AA flight number, most times. But whether it's an AA flight number or Alaska flight number, I can NEVER check in online, or reserve seats for these flights

I can't check in online with AA or with Alaska's sites. They won't let me check in over the phone either. I'm usually stuck in a middle seat by the time I get a seat. My last flight out of SEA yesterday they oversold the flight and the terminal employee said I had to go to the gate to get a seat assignment because he said they can't do it at the terminal. At the gate the lady said I had to wait no more than an hour before flight time to get a seat assignment. When I called customer service, they weren't even aware that I couldn't get a seat until an hour before the flight but deferred to the airport employee. No one seems to know policy or have a good, clear answer. All I want to do is log in like a normal customer and check in and get a seat.
I stick with AAdvantage because that's where all my miles reside. Getting an Alaska number doesn't make sense, unless there are some other good suggestions.
Does anyone have a workaround for this? Thanks.