Any of the TGV you could use on the 19th are all booked out.
Unreserved options are quite long.
09.06 Narbonne (train starts at Cerbere at 07.26 if that is a better starting point for you) - Avignon 11.28
12.11 Avignon - Valence Ville 13.22
14.17 Valence Ville - Annency 17.15
There are similar journeys from Narbonne at 10.09, arr 18.15, 12.09 arr 20.15, 13.09 arr 21.07 and 15.09 arr 23.07
Chamonix is a good deal further in time anyway.
on 25/8
05.56 Chamonix - Saint-Gervais-les-Baines 06.39 BUS
07.33 Saint-Gervais-les-Baines - Annency 09.06
10.43 Annency - Valence TGV 13.33
14.00 Valence TGV - Narbonne 16.13 *This train requires reservations and currently has space at €20/seat
09.55 Chamonix - Saint-Gervais-les-Baines 10.40
10.49 Saint-Gervais-les-Baines - La Roche-sur-Fouron 11.37
11.42 La Roche-sur-Fouron - Annency 12.16
13.43 Annency - Valence TGV 16.33
17.09 Valence TGV - Narbonne 19.20 *This train requires reservations and currently has space at €20/seat
TGV reservations can be done at https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish
There are a few options by boarding the TGV in Montpellier :
- TER Narbonne - Montpellier St-Roch 10:09 - 11:09
- TGV Montpellier St-Roch - Valence TGV 11:57 - 13:06 10€ per seat
- TER Valence TGV - Annecy 13:27 - 16:15
Also possible 2h earlier or later.
Btw did you really use your inbound/outbound day or not ? If you only activated it by mistake you could contact customer support ASAP to try getting it back.
And for the return journey there are more options via Lyon :
- TER Chamonix - St-Gervais 09:55 - 10:40
- TER St-Gervais - La Roche sur Foron 10:49 - 11:37
- Bus La Roche sur Foron - Bellegarde 11:54 - 12:45
- TER Bellegarde - Lyon Part-Dieu 12:55 - 14:22 (also possible to leave Chamonix 1h earlier for a better margin)
- AVE Lyon Part-Dieu - Narbonne 14:30 - 17:29 10€ seat reservation (available at RENFE ticket counters only) or 22€ 2nd class/27€ 1st class ticket (online)
Later option :
- TER Chamonix - St-Gervais 11:55 - 12:40
- TER St-Gervais - Bellegarde 12:49 - 14:42
- TER Bellegarde - Lyon Part-Dieu 15:55 - 17:22
- TGV Lyon Part-Dieu - Narbonne 18:09 - 21:01 20€ per seat