I supose is the only way even if i upgrade my theme.
This has nothing whatsoever to do with upgrading a theme.
The only way to eliminate advertising placed by WordPress.com on your blog is to purchase the No-Ads upgrade. http://en.support.wordpress.com/no-ads/
However, you have not been clear about where the ads you see are and what they are like. That's important because they could be coming from malware via a browser add-on.
If the ads you see are found at the end of blog posts then what you are seeing is WordPress.com generated advertising.
WordPress.com does not use text enhance or text link ads or pop-up ads or links in comments. If you are seeing those then that’s a browser-ad-on issue, or in some cases, it’s embedded into free games downloaded from the internet. See here: Bloggers: Beware of Adware. http://onecoolsitebloggingtips.com/2012/09/14/bloggers-beware-of-adware/
If what you are seeing whenever you save or update a post or page is an automatically added code/script block at the end of posts and pages that you can’t delete then see here: Malware Targets Macs and Windows PCs http://onecoolsitebloggingtips.com/2012/10/02/malware-targets-macs-and-windows-pcs/