Defective Malawi Cane chairs

I purchased a Malawi Cane 2 seater bench plus a chair from Deco SA. I paid R3499.10 on 27 November 2020 and both items were received on 11 December 2020 On 15 January 2021 I contacted the Sales & Marketing manager to inform her that the bench had developed brown mold marks all over it Both items are under cover in a protected area, with no rain or sun. The company very kindly sent me a new bench on 4 February 2021. I then noticed that the chair had also developed both brown and green mold on it. I informed the company and requested that all three items be collected and to refund me, as I was very concerned that mold would occur on the new bench. I was informed that the company had obtained a new supplier for these items so this problem would not occur in the future, but that they were not prepared to refund me for the defective items. My neighbour has had Malawi cane chairs for the last two years situated in the same position as mine, but hers show no sign of mold I understand that the company does not wish to refund me for the defective goods as it will cost them to collect the items. I don't feel I should be penalised because of this At the very least, the company could offer to pay to have the furniture cleaned and then sealed to prevent mold growing in the future