Refund or exchange refusal for brand new clothing

I bought 5 dresses from Forever New for my Brides****s. 4 of these dresses I purchased in Mall of Africa, further on I had to locate the other needed sizes myself. I had to get the other needed size from Cavendish Mall in Cape Town. I am still needing 2 of the SAME dresses which Forever New cannot help me with. I went to Woodlands to try and Exchange these 5 (all SAME dresses) with all tags in place, all slips in place, in the same bag and packaging AS PURCHASED, for something else in the store to the same amount or EVEN HALF! They refuse. Please tell me what am I supposed to do with 5 of the same dress, brand new, R7000 worth of dresses????