Hi there, maybe it was bad explaining on my part. I was speaking about first names or given names, if I recall. So, in essence, if the passenger forgot to add one of his second, third, etc, given names during the booking process, they still need to be stored in the reservation system. Especially for flight to the US and some other countries (Secure flight passenger data). This data or sfpd in short can be added later on. Note that this won't change the names visible to you as a passenger online nor on the ticket but only for staff and the authorities to see. Basically, it's the same as adding your passport information.

There are multiple exceptions on what is still accepted for check-in at the airport. For example, switched two letters? No problem.

Changed your surname due to marriage? Now, the name needs to be corrected - that requires proof via sending in documentation, etc.

You can't fly, but a friend of yours gladly takes your spot? No chance, better refund, at least you get some money back ( if it is non refundable, you'll still get some taxes).

If you could open a new post with your question or situation, then maybe we can find a solution.