Two Organizations, Two Monthly Bills, Why Sharing the Same Zoom Link

We are sister organizations, and we both pay monthly Zoom bills.  When we sign on, we have different user names and passwords -- but we share the same Zoom link.  Consequently, we cannot hold separate meetings at the same time.  Our Zoom accounts were set up by someone(s) no longer associated with us -- so we're not sure why things are the way they are.  How can we change the Zoom link for one of the organizations?  And is there another way to solve our problem?  Thanks for any assistance!