Giving Feedback?

I have used a number online clothing sites and most of them give a place to make comments about what you liked and didn't like about what you received to help them the next time they send you something.  I'm guessing this is an automated system that sends you clothing based on size and not on any feedback mechanism?  The sports bras theyve sent me so far are cute but too narrow across the chest area and not supportive enough - long straps and loose.  I could never actually work out in them.  But how do I make a request for a change to this in the future?