How do you catch rid of soap stains? I just bought a pair of American Eagle sweats for 40$, my...

I just bought a pair of American Eagle sweats for 40$, my sister wash them and now there's what looks like gray/black smudges down the front, that smell strongly of the soap, and surface soapy. I tried re-washing the pants, but it's still there. I'm pretty angry, how do you gross these "soap stains" go away?
Answers:    Spray undiluted white vinegar onto the stains. Vinegar breaks down soap. Gently dab the stains to aid the vinegar work better. Spray a little more vinegar and then launder again. The vinegar smell dissipates as it dries.
purify them with more soap in really hot water