Good day, I bought a water pump from autozone secunda mpumalanga on Friday the 11th of February 2022 and was installed on the same day yesterday it making huge noise and when we removed it we realized that it's broken

Good day, I bought a water pump from autozone secunda mpumalanga on Friday the 11th of February 2022 and was installed on the same day yesterday it making huge noise and when we removed it we realized that it's broken. Today 11:15 we returned it for a replacement but I was told by the sales people that I must pay for the replacement because of company policy, and I did pay. Why is that?