Principal, AP, and faculty frequently require my Tech Experience. Should I stop?

I’ve been working at a school in Texas as a music teacher for the past three years. And I am now known as “the tech guy“. there have been many occasions where I’ve been asked to set up audio equipment for assemblies earlier than my contract hours or to fix equipment without any expectation of reward. I’m often the first person people go to whenever they have technology problems or if they need help using some sort of software that the school has told us that we need to use. It’s gotten to the point to where I’m often spending time outside of my contract hours helping others with their technology issues only to receive a “thank you“ for all the things that I helped them out with.

I’m starting to feel like I should’ve never told them about my technological capabilities, but now I feel like I’m at a point where if I say I don’t want to help anyone out with their technology it will be seen as me being hostile. I enjoy helping people out, but now that it’s an expectation, I’m a little bit upset that my talents are being made use of without any compensation or any recognition.

What should I do?