Originally Posted by
Unterwegs
You cannot 'add' the baby to your ticket, you need to buy a completely new ticket.
I dont really understand the exact context of your reply. Do you mean that technically an infant gets its own ticket even though it is a lap child? In other words OP needs to buy an infant ticket for the baby? Agree 100% with that.
Or do you mean that in OPs situation, they will not be able to buy and link an infant ticket to the OPs original booking? Here I would disagree - this should be possible, but since the baby only travels one way, the reference price would be one-way F. The OPs call centre discussion seemingly confirms this too.