I got the call!!

One of my dresses is in!!!!!!!!!! They told me I have 30 days to pay the rest off... Has anyone ever heard of this? What could they do if I don't pay it off in 30 days? I told the girl that I didn't plan on coming right away to pay it off because the store is in New Jersey, but she said I really should to makes sure the dress is the right one and okay, but I can't see it unless I pay the rest of the money due.....