You can easily convert a free listing to premium or the other way around. Below image is how a free listing looks like. Viewers will only see the name of the business, address, phone and website.
To make a free listing into a premium go to your site's dashboard > Listings > All Listings. Hover your cursor to the business you would like to convert into a premium listing then click Edit.
First mark the check box for Premium in the Categories section located on the right side of the page.
Then add the rest of the information needed in the custom fields. You can add a coupon of a special offer of a business and a video if they have as well. Below screenshots are the information needed for a premium listing.
To edit the information in the custom fields make sure you click the "update" button of the specific custom field when done. You can check the tutorial on how to edit business information here.
On the other hand if you can delete any field you don't want to add for a listing.
Lastly once you are done adding more information and/or editing click the main "Update" button on the right side of the page. Below is an image of how a premium listing looks like. When a viewer clicks on the "more info" or "coupons" they will be taken to a page to see more information, coupons and video.