too many users on a well what can you do

I inhereted a place were I own the well,( its on my property) my father let 2 other people hook up to it years ago,(they bought the property from the neighbor who was already on the well) there is low pressure and in late afternoons sometimes none at all, there are no legal papers that I have found so far, also there water line is bigger than ours. My father let them hook up for free(uggghhh)can you believe, I'm suspecting the neighbor sold them water rights and kept the money and has copies of the easments, pretending to own the well( they all live at the end of our road) what can I do ,I just want good water pressure again