Cell phone refund, vodashop vaalmall vanderbijlpark

Hi, I bought a cellphone for my mother on the 4th May at Vodashop Vaalmall Vanderbijlpark, unfortunately my mother doesn't like the brand which is Vivo Y19 and she asked me to buy her something else with that money. I went to the shop today for the refund. The shop manager refused to give me the refund, he said he can only refund only if the phone is malfunctioning. I told him that I didn't use the phone at all everything is still as I bought the phone. Please assist me on this regard, my mother doesn't want this phone.