Send more WooCommerce fields to list

Hi,
I have added an additional (birthday and cellphone) field to checkout page, I would like to snyc this over to mailchimp.

What filter will can use for work it?

I added this filter in funtions.php, but it doesn’t work

add_filter( ‘mailchimp_sync_user_data’, function( $data, $user ) {
$data[‘MMERGE5’] = $user->nacimiento;
$data[‘MMERGE6’] = $user->cellphone;
return $data;
}, 10, 2 );