First of all, how many characters are wrong?

I did numerous correction before with AA and very simple. Just goto AA website tomorrow morning and find Live Help Chat.
Make sure you prepare your booking number. Once reach your turn, tell him/her what went wrong and the correction that you wanna make.
Im not really sure if they also limit the number of numeric alteration that you can make before charging you extra.
I usually make name correction and was being told I can only change up to 3 characters. Anything more, there would be additional charges.