Good afternoon Estelle Desplats and welcome to the NS Community.
No, I'm afraid it's not possible to adjust the information on an E-ticket once the purchase has been completed. You will have to purchase a new ticket with the correct information.
If you haven't opened or downloaded the original ticket yet, it may still be possible to block and refund it, even though officially that's not allowed. You can contact our Customer Service for this indeed, by phone, via Twitter, Facebook or chat. You can find all those contact details here.
If you haven't opened or downloaded the original ticket yet, it may still be possible to block and refund it, even though officially that's not allowed.
Why is that not allowed? A refund for a product that you bought but never received (you have no code) is simple enough and will be accepted. I did it many times (for testing purposes), no questions asked.