Legit clothing bad attitude and service

I have bought a lingerie bodysuit underwear from legit store in polokwane limpopo mall! and i didn't check it while i was in store when i got home when i try to fit it i realise that the under button pins were 2 instead of 3 and the remaining ones were very loose when i took it back they told me they dont exchange underwears as if its my fault while it's their own factory fault! please help me what must i do?