Tried searching but everything is from 2014 at the latest.

I'm trying to make a booking (revenue) including an infant (under age 2) but by booking a seat for the child instead of lap child.

Online, when searching for infant, it only includes child as lap child. When searching for "child" (age 2-11), when it comes to adding the birthday, it errors that the birthday doesn't match the ticket type.

I found it through ITA Matrix but inputting it into bookwithmatrix.com also didn't work, nor did Hipmunk.

I gave up and called the local AF number and the quoted price was outrageous. Online, ticket was $630/person. Even without a child discount, that would be under $1900 for 3. The agent offered 2 adults for $1900 plus the 3rd ticket, bringing the total to over $2500!

Any suggestions for how to go about this?!