How do I get a license for the Google Maps API to work?

I am creating an application that will require over 5000 calls per day for the Google Distance Matrix APIs. According to google docs, you cannot exceed 2500 google maps api calls per day at no cost. What's not obvious is the pricing plans and payment methods available. I see something related to the number of map downloads (25000+ per day) and the charge associated with it, but nothing related to calls through various google APIs. I see that if you make more than 2500 API calls per day, you must purchase a Google Maps API license in order to work. That's fair enough, but it doesn't tell you how to do it or what the pricing plans are. Am I missing something principled and obvious here? I didn't have much experience with the Google Maps API. Overall the API and documentation are definitely excellent,but I am confused by this. 2 days ago I sent a message to Google Sales but I didn't get any response. Any advice would be appreciated.

thank