My parents dont understand how hard i work for stuff!?

Whenever I want something, they ALWAYS

let me down. I work sooo hard for everything

I do. Like today:

My brother and I are working together for something and now I can't cause he already invited his stupid friend over, and my brothers friends mom said its "okay" if he needs to do it. Then my dad yells at me and says HE MADE A COMMITMENT! YOU HAVE TO NO MATTER WHAT SHE SAYS! And then, when I tell my mom how hard I work for stuff, and she says YOU ONLY CARE ABOUT YOURSELF! YOU NEVER THINK OF OTHERS! THAT IS ALL YOU CARE ABOUT!

I am a very hard working person, and I DO care about other people. I an a very nice girl and I have a lot of friends. My mom even called me a FRIENDLESS SELFISH BORING BRAT and I only want to work hard for things. Please help me. I wanna know hiw this could stop! And so they know Im NOT a selfish brat, and im NOT trying to be mean.