CrudField JavaScript Library with relationship/subfield fields

I have a crud with a relationship type and subfields:

'name'  => 'serviceProvider',
'type'  => 'relationship',
'label' => 'Services Provider',
'subfields'   => [
    [
        'name'  => 'cost',
        'label' => 'Cost',
        'type'  => 'number',
        'attributes' => ["step" => "any"], // allow decimals
        'wrapper' => [
            'class' => 'form-group col-sm-4'
        ],
    ],
    [
        'name'  => 'is_no_tarif_cost',
        'label' => 'Cost without tarif',
        'type'  => 'checkbox',
        'wrapper' => [
            'class' => 'form-group col-sm-2 d-flex align-items-end'
        ],
    ],
]

and I want to make it so that when the field is_no_tarif_cost is changed, a console log of the changed rowNumber

crud.field('serviceProvider').subfield('is_no_tarif_cost').onChange(function(field) {
    console.log('hey i am here on row: ' + field.rowNumber) 
});

I did everything according to the documentation, but it doesn’t work. No JavaScript errors in the console. It’s as if the hook is being hung on the wrong object. Any ideas what the error might be?