buisiness on shabbot

Question

hi recently i started a store on ebay.com im sure you are famaliar with the site however im wondering if there is a problem since im doing buisiness on shabbos i dont have auctions ending on shabbos but theres the buy it now option and saturday happends to be the busiest day on ebay i also recieve payments on shabbbos however of course i dont ship out thee item on shabbos. does this fall into the catagory of doing buisiness on shabbos ? thanx