Unfair exchange practise

I Bought stationery on 17 December2023 at pna silverton on the 18 December 2023 I went back for exchange to my suprise they day their policy doesnt allow exchange all they do is refund that youll get within 7 working days. I insisisted on the exchange because i didnt want to come back again but my plea fell on deaf ears. To my suprise the policy they are talking about its not written anywhere on the receipt, the only info that is there is to say all exhchange and refunds will be done within 14 days meaning if you come after 14 days no exchange or refund will be done