Cross Selling
Cross selling is when an existing customer is offered and sold ancillary / additional services or products. One example is selling a credit card to a customer with saving account.
Banks give utmost importance to cross selling because it is generally a low cost affair to sell an existing customer than to a new customer. Cross selling is taken as a transaction based activity but more as a relationship building exercise by the banks. It helps better leverage of the available resources and existing clientele base.