Faulty Phone

We bought a cellphone on the 28th of August 2022 at Mr Price Dayizenza Plaza, ehen we go home the phone couldn't open and we took it back on Wednesday 31 August. They told us that the person who sold us the phone was not around, they will call when he is at work the following day. They said we should leave the phone with them. What infuriates me is that we returned the phone within the 7 days of exchange and they refused to exchange saying they have to send it to ve fixed. I paid cash for the phone, today I have no phone and they took my money. What kind of ******* is this. It is faulty exchange it or give me my money back.