Laundry Soap in My Kitchen Sink - Not Good at All

This keeps happening. I get a backup in my sink, and it is laundry soap that comes up. Well, being this is TOXIC, it's kind of a big deal, yet after complaining several times not one thing has been done to stop it. It is most likely someone above me in the building washing things by hand in their sink and using a lot more soap than needed. I am getting seriously tired of having to scrub down my sink two or three times a week, because some random person is not doing things the way they should. There is a big sink in the laundry room for just this task, yet they do it in the same place they wash their dishes. Sigh. You just can't fix some things, like the lack of presence of mind it takes to do this. I used to know a guy who did his washing in the bathtub to save the $3 it took to do a load of laundry in that building. However, here it's as of this post, included in the rent, in a couple of months, they will be tacking on a $10 fee for the laundry, if you use it or not. That alone has some people upset, as they send their stuff out. I'm full on willing to pay $10 to do the was when I want, and not have to mess about with change to put in a machine.