Cross-selling
Appearance
Cross-selling is the strategy of selling other products to a customer who has already purchased (or signaled their intention to purchase) a product from the vendor. Cross-selling is designed to increase the customer's reliance on the company and decrease the likelihood of the customer switching to a competitor.
Companies such as IBM also use the term 'attaching' to refer to the practice of selling other IT products at the same time as the principal product purchased by the customer. These additional products are often components of the same system as the principal product.
References
Academic papers: