Apple Card installment Apple products

I bought I phone 12 with Apple Card as the representative in Staten Island store told me that buying with Apple Card will be with same price with no interest

so know after I bought it the Apple Card told me to avoid interest they have to receive a contract by installment from the store

and you don’t give me contract you only told me there is no interest for Apple products paid with Apple Card

so I need solving this issue please as it will cost me 22% extra for each remaining balance or you return the mobile and give me my money back