sans devoir passer par le vendeur...

Hi Enotet, bill as in billing, I would say, since it says it's an invoice service. I would imagine the "user" they are talking about is buying photos, can you confirm?

My interpretation of the little context provided is that the user chooses an image they want to buy and does not have to talk to the sales rep to pay for it, they can pay for it directly through the system. Although I'll wait for your confirmation, I am confident of this interpretation, however I'm not that confident on the French word for it though, since I mostly work Fr -> Eng.

C'est mon choix.