I would like to get a refund.
或者直接说.i want to return this.
refund就是退货的意思.
店里的很多商品上都会注明:No Refund.就是买完以后不给退的.
所以建议你用第一句.
I want to refund the clothes.
退钱是refund,退货是return
可以说
I would like to return this clothes.
一般来说,final sale(清仓处理)的东西是no return 或者 refund 的.