While I have done some searching, I have not yet found my answer. Hopefully, someone has some greater AA codeshare on IB experience than I.

I have booked a TATL through MAD on an Iberia operated AA codeshare. With my AA record locator, the IB site cannot find my booking. When I call the EXP desk, then give me a _five_ character reference as my Iberia record locator. The site explicity instructs that record locators have six characters.

Bottom line is that I like to be able to change/select my seat online, if possible. If this is not possible, will either of the reference be known to an IB agent? What is the best way on going about this?