Unfair/unreasonable protocols followed

I have a problem here with regards to a cellular phone I bought at Ackermans Soweto Protea Glen on the 25/02/2024 whereby I was advised that if I encounter a problem with the phone within 7 days, I should bring it back then I'll get a new one but that wasn't the case when I brought it back on the 03/03/2024 just as the consultant first told me that the phone was brought after 7 days which does not make sense because if you start counting from the 25/02/2024_14H00 until the 03/03/2024_13h30 you'll realise that the phone was brought back within 7 days and then with regards to the phone, the consultant didn't even bother to check what problems does the phone have just as at times it'd freeze or the screen would be dim but sometimes visible so those were the problems I was getting which weren't physically caused by me but instead of getting a new phone , my phone was sent for repairs so I'm really furious as to who must pay for these repairs because I'm supposed to be getting a new phone not dealing with repairs because I didn't break the phone. Please kindly assist me with this matter, It's really unfair as to why do they even have these 7 day guarantee/warranty if they are always going to give issues when we have to claim within these guarantees/warranties and I bought this phone cash