head over heels

bought a top for R150 . on the 10/02/20. the shop assistant gave me a size and told me that it would fit. i was in a hurry so just trusted her judgement and took it. the next day i 11/02/2020 i took it back to return it and the refused to give me back my money., said they have a no refund policy. i think this is unfair. i took it in the next day because it didn't fit