How long have you had the bag? Are you close to a LV store to take it in? I am sorry that happened. I do not own the galleria but have never had a problem like that on any of my bags.
This has happened to someone else in the Galliera clubhouse I believe. I do know it happened to my gf denim daily.. She took it to the flagship store and they fixed it without a problem..
Good luck with the repair, let us know how it goes!