button calls every ajax requests made before

Hi there,

in my table are buttons in the last columm, made with render: and createdcell: the function calls a ajax request.
Button clicks calls the the function, but the ajax request ist called for every previous call.

I found some solutions with .off() or unbind() but nothing seems to work, or i dont know how to use it right.

Here is the table and ajax code:

var open_events_table = $('#TabelleOffen').DataTable({
    responsive: true,
    paging: true,
    searching: true,
    processing: true,
    language: {  url: 'dtgerman.json' },
    dom: "<'row'<'col-sm-3'l><'col-sm-3'f><'col-sm-6'p>>" +
     "<'row'<'col-sm-12'tr>>" +
     "<'row'<'col-sm-5'i><'col-sm-7'p>>",
    ajax: "term-abfrage.php?oTermine=1",
    columns: [
    { data: 1, title: "Datum 1"},
    { data: 2, title: "Datum 2" },
    { data: 3, title: "Vorschlag" },
    { data: 8, title: "Ort"},
    { data: 10, title: "Art"},
    { data: null, title: "Maps",
        render: function(data){
            stylebutton = "<button class='btn btn-sm btn'><i class='fa fa-directions'></i></button>";
            return stylebutton;
            },
        createdCell: function(cell, cellData, rowData, rowIndex, colIndex) {
            $(cell).off("click.cellClick").on("click", "button", rowData, get_maps); }
    },
    { data: null, title: "Bewerben", 
        render: function(data){
            if (items.includes(data[0])){
                stylebutton = "<button id='"+data[0]+"' class='btn btn-sm btn-success'><i class='fa fa-minus'></i></button>";
            } else {
                stylebutton = "<button id='"+data[0]+"' class='btn btn-sm'><i class='fa fa-plus'></i></button>";
            };
            return stylebutton;
            },
        createdCell: function(cell, cellData, rowData, rowIndex, colIndex) {
            $(cell).on("click", "button", rowData, book_event).off("click.cellClick"); }
    }
    ]});

function book_event(event) {
    event.preventDefault();
    var welcherbutton = event.data[0];
    if ($(this).hasClass('btn-success')){
        var status = 0;
        $(this).removeClass('btn-success').children('i').removeClass('fa-minus').addClass('fa-plus');
        $.post( "term-abfrage.php", { addtermin: 0, user: user, terminID: event.data[0] })
            .done(function( data ) {
            //alert( "Data Delete: " +  data['meldung'] );
        });
    }else {
        $('#distmodal').modal({backdrop: true});
        $(".modal-footer > button").click(function() {
            clicked = $(this).text();
            if (clicked == "Bewerben"){
                dist = $('#distkm').val();
                if(!dist){
                    alert('Kein Entfernung angegeben!');
                } else {;
                    $('#'+welcherbutton).addClass('btn-success').children('i').removeClass('fa-plus').addClass('fa-minus');
                    $.post( "term-abfrage.php", { addtermin: 1, user: user, terminID: event.data[0], dist: dist })
                        .done(function( data ) {
                        //alert( "Data saved: " + data['meldung'] );
                        $("#distmodal").modal('hide');
                    });
                }
            };
        });
    };
    return true;
};

LG,
Ennox