You must use WP_Query to query the “accounts” post type using a meta query to query by the “bank” relationship field.
// simplest form
$args = array(
'post_type' => 'accounts', // replace w/your post type
'posts_per_page' => -1,
'meta_query' => array(
array(
'key' => 'bank' // replace with your relationship field name
'value' => '"'.$post=ID.'"', // global post ID of current post
'compare' => 'LIKE'
)
)
);