It sounds like you have an auto relist profile associated with your listings which, after it has been applied, will relist your items as per the profile when they close on eBay. If this is the case, you can see it on the Active Listings page of your Auctiva account - the listings with such a profile added to them will show this. To end an Auto Relist profile you need to select the listings where you no longer wish to use the profile from the Active Listings page and then click on the "Stop Auto-Relist" button near the top of the page to end the profile. When these listings next end, the profile will no longer be applied to them.
If you have other questions or run into any difficulty with this, please feel free to file a support case from under the Help tab of the site (which is where the link that Jacob provided leads) and our support team will be happy to assist you further.