Bad Attitude/Service/Bad Quality

On the 26th June 2018 I bought a dress only worn it on the 7th July 2018. Then the threads on the slit came off. On the 31st July 2018 I went to the store to return the defect dress Evelyn and Rebecca at Edgards Kolonade gave an attitude. Then Sizwe came to assist , I didnt have the slip but bought on account . The dress is now on sale they want to give me a refund on a sale price . The have a slip on their sid eshowing how much I have paid for the dress apparently its only for your records. if I have paid cash I will understand if you give me a voucher and tge sale price as you dont have proof of how much I have paid. I bought on account and its your faulty dress which was not my intentions to return it hence I dont know where I have put my slip. Now I have to shoulder your mistakes. Am closing my account thank you Edgars.