Originally Posted by
VegasGambler
Your seat will almost certainly stick unless there is an equipment change or something. No chance you will be asked to pay at check in. Worst case, you get moved and have to pay to move back.
I've had AS ask me to pay for upgrades on check in when I selected premium seats in the app. In my case, I just showed my AA status and the agent manually waived the charge, but if that happens and OP doesn't have status, they may have to pay. Something about the AA/AS integration is a little wonky IME.