We fly every month with our infant and every time it’s a 3 hour hold to get it done. They have cut off the call back feature unfortunately, and I have had the same experience you have with the text help.

I haven’t dared try adding at the check in desk, but I’d bet they could do it there. It’s just nice to have it done beforehand. I wish they’d let you do it online…most of the other airlines do.