Incorrect size label on bra

I already had 1 tri-action bra, size 36 (light purple) and about a month ago decided to buy another one, also size 36 (navy & orange). Two weeks ago I decided to buy a 3rd one (black) size 36, however it is remarkably smaller than the previous two. I didn't try the black bra on before purchasing it, as I already had recently purchased and already owned size 36 bras that fit. The shop I purchased the bra from doesn't return underwear. I paid R380 for a bra that's the wrong size and I can't wear.