Family Dollar

I purchased a bra set that included two bras. When I arrived at home I took both bras of the hanger. After doing that I realized they weren't gonna fit
I did not try them and on and I still have the price tags that was on it. So my question is why can't I return and get my money back? I think if it can't be returned then it should be written somewhere on the receipt or somewhere in stores about the return policy. It shouldn't say you can return within 30 days with receipt because that's false advertisement. I can't return my product even though I have receipt and its within the first 30 days..