Is this in the Desktop app? If it is the desktop app, does the title bar say "Spotify Premium" or just "Spotify?" If, since you've purchased premium, you've not logged out and back in to the client, you may need to do so. Spotify may not see your upgraded account status unless you log back in. If this doesn't work, you may need to contact Spotify support for help sorting out your account.
Thanks. I've done this already. I hope they reply as they didn't for my last inquiry, which was when I tried to buy premium and couldn't (at least according to your site) and then discovered that it did go through when I checked my e-mail. My mobile work but still see the ads on desktop.