Upvote:4
There's nothing in their terms and conditions which forces you to exchange your ticket at the departure station. If you don't want to physically go to a train station to exchange your ticket, you can also do it online.
The only drawback is that you'll have to pay a fee depending how long before the scheduled departure you exhange your ticket :
From their website ("Exchanges & refunds" part, bottom of the page):
Exchange any Loisir or Loisir Réduit ticket free of charge or get a full refund up to 31 days before your departure. If you request an exchange or refund 2-30 days before your departure, you will be charged a fee of €5 per person and per journey On the day before and the day of departure, this fee increases to 40% of the ticket, up to a maximum of €15 for TGV travel and €12 for Intercités trains requiring reservations. Once the train has departed, Loisir tickets cannot be exchanged or refunded.
I've never changed a TGV ticket but I've often bought a TGV ticket from city A to city B in city C's train station.
Upvote:5
The restriction on exchanges at departure stations only is for flexible fares (Pro) which can still be exchanged or refunded a little bit after departure time.
You can exchange the ticket up to one hour after departure using the TGV Pro app (which is quite restrictive).
You can exchange or get a refund up to two hours after departure at the departure station.
This is to avoid people exchanging the ticket after having actually "used" it without a check having been performed, which is really easy on some short trips like Paris-Reims (45 minutes), Paris-Lille (1 hour), etc.
Before departure, you can do exchanges via any of the channels (online, mobile, phone, train station...), with the specific restrictions for your fare.