Gvonne Oolagong is a one-off character played by Liz Dubberley in Chapter 31: Jeremy Bearimy. She is the checkout clerk who deals with Chidi's shopping and is nonplussed when Chidi attempts to give away first his credit card, then his car.
Her name is a spoonerism of the Australian tennis player Yvonne Goolagong. Although given this name in the end credits, during the episode her name badge clearly reads "Rose".