Rights of customer

i bought a bag yesterday. the manager of the shop never explained that i will not get my money back. today i return the bag and i was told that i can't get my money back due to no refund policy. i asked the lady why did she not explain to me yesterday and i was told she does not have to explain to every customer that she serve. i don't understand why do i have to be forced to keep something that i don't want. i have a witness that she never explained. in the china mall they can get away with everything because they are untouchable. so we as customer should be abused by people like this