I feel ripped off

I did watch my little sister and my parents know it but not they're trying to deny it. I was watching her right in front of them. I played with her outside, watched her at Target, played with her at home when Sarah was being all weird with her friends, and other times but my parents just don't want to pay me so they're saying it never happened. Oh and she said that right when she came home I wasn't watching Emily. WHAT A FREAKIN LIE! I was playing with Em in the wagon and even helped mom unload the groceries. What a big fat lie! I feel ripped off! I should get paid and mom even said today that she would pay me. God damn it! Well don't expect me to watch my sis again, cause what's the point? My parents will just end up denying that it ever happened just so they don't have to pay me.