Takealot ******

I ordered a lingerie body suit, instead of sending me a size XL as I've ordered they sent a size M, I logged for a return and explained the reasons, understanding very well that it's not returnable but they accepted it back and scheduled for collection, I didn't even try to fit it in I packed it in its original packaging, now when it reached their warehouse, they decided that no they can't accept it they're sending it back to me, the small size they sent me in the beginning. What about my money? How is that my fault when it's clear which size I ordered on the order history?? What am I supposed to do with it? Why don't they account for the mistake they did?