I'm in the same situation. I've made AA award reservations for Qatar business class. I'm trying to add a lap infant ticket to my reservation. Qatar Avios club agents say I cannot simply buy a revenue ticket for the lap infant using cash and link the PNR to the parents' PNR. I called AA, who say I have to call Qatar. It seems someone was able to do so via an AA agent: https://www.reddit.com/r/awardtravel..._is/?rdt=52985