refund of dropbox subscription

trialled Dropbox for one specific purpose of sending a video taken on my phone - it didn't work. I forgot to cancel subscription details I had to add for trial. I've been charged! I've gone into iTunes and now cancelled the subscription. There auto response from my request for refund is 'NO'. I want a refund because I have no need or intention of using Dropbox again - it couldn't even do what I wanted it for!