Returning a cellphone for a different phone

On 17 January 2026, I purchased a cellphone on credit and now just not happy with it's performance. I Tried to return it on the 7th day (24 January) for exchange even if I take one of the popular brands Samsung, Oppo etc at a higher price than the cheap brand I took. The store refused to take the phone saying I didn't take insurance on the phone. If the salesperson had asked if I need insurance on the phone, I would have taken it. It just didn't cross my mind at the time. Secondly, I was told the phone can be sent for repairs at own costs. I told the sales person the phone is not faulty, Im just not happy with how it performs, it's a very cheap brand and poor quality which I was not expecting. So, I only want to change the phone as I'm not happy with it. The store refused and I don't know what to do next.