According to MSDN ReportConsumableFulfillmentAsync is Windows Phone 8.1 API, so you cannot use it when creating Windows Phone 8 apps. Stick with ReportProductFulfillment and Windows Phone 8 apps for now, it will take some time for Windows Phone 8.1 to get on the market
Only for consumables
If your are looking or a nice in-app wrapper, take a look at this https://github.com/igorkulman/Kulman.WP8/blob/master/Kulman.WP8/Services/WindowsPhoneStoreService.cs