Email to contact

https://www.apple.com/contact/

If it says processing, that means it's being assembled in China and will ship when it's ready, first to your country at which point it will change to Preparing to Ship, then it will ship to your address via local carrier (FedEx in the US), usually overnight.

Basically, Apple gave you a delivery window of a one-week period when you placed the order, and that's when you can expect the Mac. The Processing step is a long one, Preparing to Ship to being in your hands is ~3 days.

Yes, they don't charge you until the item actually ships.