Bad customers service from payjoy

I bought a phone at payjoy on the 05/09/2023 When I arrive home I calculated the interest that I will be paying more than the actual price but for short period of 6mnths.I sent them a email wanted to cancel I did that within 1 day of the purchase. I request a refund since I have never used the phone. I was advised that I won't get the refund. Please help me to cancel this offer and get my refund.