AJAX call being canceled when submit button is used

I'm fairly new to programming, and I'm trying to fix a slight bug I've encountered. My data is supposed to be posted to the an API when I press the submit button, but when I use the button, the page just refreshes. When I preserve the logs from the console, I can see that the call IS being made, but it's being canceled before it can be posted. I'm using a live server to test out my code.

let URL = "https://6327494d5731f3db9956d362.mockapi.io/users";

$("#submitButton").on("click", (event) => {
  if (event.preventDefault) {
    let firstName = $("#firstName").val();
    let lastName = $("#lastName").val();
    let emailAddress = $("#emailAddress").val();
    console.log(firstName, lastName, emailAddress);

    $.ajax({
      url: URL,
      data: JSON.stringify(firstName, lastName, emailAddress),
      dataType: "json",
      type: "POST",
      contentType: "application/json",
      crossDomain: true,
    });
  }
});

Thank you in advance for any suggestions.