Customers change order status from completed to processing

i think this function is responsible, please what should i modify to avoid this problem

add_action( 'woocommerce_thankyou', 'cheque_payment_method_order_status_to_processing', 10, 1 );
function cheque_payment_method_order_status_to_processing( $order_id ) {
    if ( ! $order_id )
        return;

    $order = wc_get_order( $order_id );

    // Updating order status to processing for orders delivered with Cheque payment methods.
    if (  get_post_meta($order->id, '_payment_method', true) == 'cheque' )
        $order->update_status( 'processing' );
}

• This reply was modified 3 years, 7 months ago by khalil43.

Solved by using this code instead of the first

//change order status cheque to processing
  add_action( 'woocommerce_thankyou', 'cheque_payment_method_order_status_to_processing', 10, 1 );
function cheque_payment_method_order_status_to_processing( $order_id ) {
    if ( ! $order_id )
        return;

    $order = wc_get_order( $order_id );

    // Updating order status to processing for orders delivered with Cheque payment methods.
  global $product;
$order = wc_get_order( $order_id );
    if ($order->data['status'] == 'on-hold')
	{if (  get_post_meta($order->id, '_payment_method', true) == 'cheque' )
        $order->update_status( 'processing' );
}}

please tell me if there is any mistake thanks