Hi Andre!
This is a common problem and I know several people that have met it.
Tips for fixing this problem:
1. Make sure that your prefered landing page are relevant for the keyword, title, H1 and content.
2. Use the power of internal links, if you mention the keyword on other pages, make a link to the prefered page with that keyword (naturally sometimes, not always). It will give Google a signal on what page you want to rank for the targeted keyword.
3. Check incoming links in OSE, if you find "good" links that are pointing to the wrong url, make contact and ask them to update the URL.
4. Make more signals by using social media-links (G+, Facebook and Twitter) to preferred URL.
Hope this will help you!