Bad Customer Service

My sister bought amplify evoke true wireless earphones at Pep Cell Chris Hani Mall Vosloorus for R159. 99 on the 7th September 2024 the cashier was Lindokuhle @ 13:41 and when she got home and tried connecting them to her phone they would connect but the sound wouldn't come through the earphones meaning the earphones and the phone are not compatible and won't communicating together. She took them back today 17 September 2024 and was told they would not refund her or take them back because the earphones "do not have a manufacturing default or defect" with that being said what is my sister to do with earphones that are not compatible with her phone?