Bad bad service

I have bought a mobicell phone from them on 18 May 2018. However I am not satisfied with the phone because I cannot download any apps. I have tried to return the phone on 20 May and they refuse to assist me in doing an exchange. According to the vodacom does not allow exchange or refund which is total b....**** because I have called vodacom and they assured me I am within my rights to do so. I just want to add that they just have this lack lustre attitude towards their jobs and customers because even when busy there is only one cashier the rest is either fiddling with the radio or just standing around