See acf/prepare_field. Using this filter you can set the default value of a field from the field on the user page.
add_filter('acf/prepare_field/name=your_field_name', 'default_user_company', 20);
function default_user_company($field) {
$field['defualt_value'] = get_field('company_name', 'user_'.get_current_user_id());
return $field;
}