Assign a new WP user role when a user cancels their membership in Paid Memberships Pro

change-user-role-on-cancel-pmpro.php

<?php

//Please copy line 5-22 into your active themes functions.php or custom plugin

//code to assign specific WP user role when cancelling
function my_pmpro_after_cancel_change_role($level_id, $user_id)
{
    //get user object
    $wp_user_object = new WP_User($user_id);
  
    //ignore admins
    if(in_array("administrator", $wp_user_object->roles)){
        return;
    }

    //if user cancels their membership, set their user role.
    if(empty($level_id)) {
        $wp_user_object->set_role('subscriber'); //choose your default role.
    }
    
}
add_action("pmpro_after_change_membership_level", "my_pmpro_after_cancel_change_role", 10, 2);