Small cut

I order 2 bras online which was R350 and they were a 42c and to me a 42c is a size 42c. when I recieved them they were too small and my other bras i got from donna clair were a 42c. i phoned the online support team and the consultant told me that it was a small cut and that i cannot return it via courier because its lingerie and you dont exchange bras. I must go to a store and TRY to return it there. This is ridiculous. i know what bra size I am and the bras that arrived were not cut correctly. I dont have a time or petrol to drive all the way to a forschini for them to tell me that they wont return it. i will go to the store if i get a guarentee that the unworn bras will be exchange for the right size