Why can’t I cancel order?

I ordered an iPhone 11 pro max 4 days ago on the 22nd. When I ordered it didn’t say out of stock but now I was told today that the iPhone is backordered until Oct 16th. I tried to just have the order changed to a color that was in stock but was told it’s not possible to edit or cancel the order because it was already processed. Guess I don’t understand why an order that is backordered and won’t ship for 3 weeks can’t be changed or cancelled so I can get one that’s in stock?