<prompt> Human: The context: Im a student at a university. I do hourly work at a student society owned venue on campus where the managers arent students. Its a technical position and Im experienced with their system. No one else readily available is trained on it. I wasnt hired, I carved out the role for myself by doing it for free then they recognized the value at which point the manager set my rate at 24h. They trust me and Im accountable. I have not signed any contracts.What happened: Yesterday I received this invoice along with a request for a credit note so that it can be applied to my next invoice. They owe me money for October! I have not responded to the email yet.It looks like my boss wants to remove the 132 they owe me for the event on Sept 28th and renegotiate hours I already worked. I also dont know where there are circles and minus signs next to two other nights I worked.My boss has a reputation of being cheap but is this even ethical or allowed or common? Shouldnt they just renegotiate my pay or hours for the next event since its monthly? They didnt say they want to renegotiate for any of the other events I worked.  <response>: I dont think he can do that. You probably wont get that money you have coming from him for your latest work. Dont give him the money hes asking for and just dont do any more work there. Sometimes in business you get a customer who is more trouble then they are worth. This guy is one of those trouble customers. Cut him loose and use your skills elsewhere. 