score:3
It's not possible to change your ticket delivery type after booking. Your only option would be to obtain a refund (if your fare conditions allow it) and then book a new ticket.
I'm not sure how good the customer service at voyages-sncf is, but for future reference you can book almost all the same tickets at my website loco2.com and we have excellent customer service for dealing with this kind of issue as demonstrated by our excellent ratings on Trustpilot.