I don't think there is anything I can do about this, but just in case someone here can help me. ... I made a reservation today for travel from Paris to Amsterdam and meant to put in 12 of September and somehow put in 13 of September. This was for the least expensive non-flexible fare. It is too late to call to try to to change it with their customer service people, so I will have to wait until early tomorrow. I think I will just have to eat the $93. Has anyone been able to change the date for a non-flexible fare? Thank you.

try to purchase the tickets for the correct date and then call in. it's possible you're stuck with a $93 slip-up

Last year we made redundant bookings at Thalys, so we emailed them, after a couple emails exchanges, we had to mail a written request to SNCF to cancel the double bookings we had accidentally made and refund money.This is where they redirected our mail-(Customer Service SNCF - 62973 ARRAS - Cedex 9 - France)
They suggested us to get hold of the ticket collector in the train itself and have him write on the ticket that we were only 4 people travelling that day not 8. The ticket checker made a note and we got our refund in 2-3 months.

Thanks to both of you; I'll try calling tomorrow and see if they suggest putting a refund request in writing.

rjain-I don't think I saw an email address on their site-do you know what it is?

This is the email address we used-
Customer Service Thalys <[email protected]
Hope this helps.

I just wanted to report back that I called Thalys this morning at the number on their site (0032 (0)70 79 79 79) and was able to change the date for out tickets at no charge and no hassle. The agent said that if you call within 24 hours you are able to make changes, even though the ticket is non-flex. I don't think it says that on their website anywhere. Hope that this information will be helpful to someone in the future.

I made a similar mistake with SNCF in France; called , emailed and sent letter, all to no avail. Had to eat the mistake; I am hyper careful now when I buy train tix online. Good luck!

Whoops, just see that you were successful; good for you!