Orders with change seller, has the respectivity order on first seller cancelled and a new order on second seller will be created. If even the new order is out of the Cancellation grace period, the user still can cancel the order.

The system nowadays has no control after the first cancellation because the Marketplace order already has one cancel confirmation (in case of first seller order), and do not control this grace period anymore.

Create an order and execute a Change Seller feature, after the second order creation wait to finish the cancellation grace period, and execute a request of cancellation as a end user. The order will be canceled at time.

On orders interactions you will see the user on request-cancel message.

There is no workaround for this case.