Change order status to Completed after the successful payment

add_action( 'woocommerce_payment_complete', 'wpdesk_set_completed_for_paid_orders' );

function wpdesk_set_completed_for_paid_orders( $order_id ) {

    $order = wc_get_order( $order_id );
    $order->update_status( 'completed' );
    
}