Worst service ever MR Price

I am furious with the service received from Mr Price at 42 boulders centre, old Pretoria rd. Halfway house Midrand. I spoke to Rosa regarding a phone I purchased on Wednesday the 4th of September. After I got home I opened the Redmi A3 and started it up. The phone froze and would not even accept my banking app. Which I had to go into the bank to sort out. Which it was the error of the phone. Today I went to the Mr price store to return the phone because I was not happy with it. And possibly pay in to get a different phone. However the supervisor at the cellphone counter was very condescending and had a bad attitude. She refused to refund me, or exchange the phone. Accord to her there is nothing wrong with the phone. There was another customer with the same phone, who also was not happy with it and needed an exchange.Where on the slip or invoice does it state that with in 7 days that at the stores discretion they can't return a product that a client is not happy with. She wanted me to leave the phone and return later. Who would have been responsible for the damage or loss if something happened to it. ? Also, who is going to pay for my fuel that I had to use to return to the store. This is by far the WORST service ever. I demand a refund, and I demand that person be fired. I will not let this matter go. Who is she to tell me that she will not return a product. What will happen after 7 days if it does break down.