KAYA FM STUDY

Hello,I need help.Human8 square invited me to do a study about KAYA FM and they promised that they will pay R500 for doing that study but when it time to pay they come up with different stories busy telling me that I didn't finish all the activities that I was supposed to finish and I ask them who's fault is that because I finished all the activities that I got on the app and they said that they reached the number they want why did they invite me when they know exactly that some activities are missing. Please help me to fight this fight I wants what is mine that I worked for I wasted my time and my data doing that study and answering those endless questions from the moderator they must pay me