Mysterious 'cancellation window'...

I made 3 separate orders with Dell.ca (canadian branch).  All were for R11 gaming desktops.  One order I tried to cancel just a few hours after placing the order.  A rep emailed me to tell me that I missed the 'cancel window' and we would have to wait until the order is invoiced (which I would apparently receive notification).  I made 2 other orders for our business.  Some days later due to circumstances changing I needed to cancel those orders too.  Again 'missed the cancel window and wait for invoice'.  I told the rep I do not want to waste resources by shipping to me and then having to return everything.  He said 'just refuse to accept the shipment at the door' and they will ship it back and refund me 'in 2-3 weeks'.

Now I get a message that one of the orders has shipped.   I tried contacting the rep again...no response.   

It honestly seems like everything from the 'cancellation window' to the 'waiting for invoice' is just giving customers the runaround instead of simply cancelling the order.

Shipping to a customer who has cancelled days and even weeks before the ship date is such a huge waste of time and resources.  

Very disappointed so far with dell.