How can I mend my model?

I have a Uni-Com Model 11575 bell push. I replaced the battery and when I went to turn the mains off and on again I found that I had left the mains switch off! I then turned the mains switch ON then off as I didn't know what else to do. The unit screeched and I couldn't do anything to stop it. I'm hoping there might be a solution.
Thanking you in anticipation.
Margaret Somers

Margaret Somers, January 2023