You should contact CGC to give them the details.
I have artists send books in all the time so I can tell you in my experience once its received someone from the receiving dept sends me an email asking for invoice details like tier, ship method, payment info etc. I have a credit card on file so I ask them to charge that, you CANNOT enter the info online anywhere. A way to work around that for next time is to fill out a form and email it to the artist and ask them to send that in with the book. That way CGC will have a invoice when they receive a book.
Barbara Turner is from the accounting dept if Im not mistaken, so the ngccoin domain email address makes sense.
HOWEVER, You should contact CGC directly to give them the details just in case. As suggested, call them.
Good luck