Upsell & cross-sell recommendations based on API software recommendations. Don’t worry about upselling, just focus on your market. Upsells & packages: Develop successful upselling, cross-selling, and promotion programs to increase sales. Build your own sales or use one of our predefined ones. Slick One Click Upsell app: Slick upsell, cross-sale, gifts, and related package packages are provided through popups. There is an Upsell in the cart and One Click is in the cart.