Some old people really piss me off

I'm a cashier and I have a stool, which I went through hell to get approved, and it doesn't work with the register AT ALL and still hurts my back... but some old people came through my line and loudly kept saying "wow, you get a stool!? I want a stool! I have to stand all day! I want one!" In a very condescending tone, not genuine at all.

And what I said was "don't worry, I had to pay $200 for it..."

But what I WANTED to say was "you can have it, along with my connective tissue disorder, POTs, and almost all of bones being in the wrong spot"

But I was more pissed because my bosses are notorious because they've done so many illegal things to me while I was trying to get any kind of accommodations and I've fought tooth and nail to be able to work and they treat me like SHIT because I'm disabled.

Not to mention that I still can't work more than 4 hours a day and three days a week...I can't work more than 15 hours because my store isn't accessible at all