cross-selling

/K R AO1 S S EH1 L IH0 NG/
verb
  1. 1

    To sell (additional products) to existing customers.

    โ€œThe sales training program on cross-selling our best customers profitable advisory services.โ€

Source: https://en.wiktionary.org/wiki/cross-sell, https://en.wiktionary.org/wiki/cross-selling