Reserve numbers before ordering. This method gives you a token to use with the POST /numbers/store/{token} method. Your booking is held for a maximum of 5 minutes. You can have only one reservation at a time: a new reservation releases the previous one, whose token stops working.
The numbers are picked at random among the available ones matching your filters: prefix matches the beginning of the number, area a part of the area name. The quantity may be reduced to the number of phone numbers your account can still have. If no number matches, the API returns 404. Prepaid accounts need enough credit for the contract duration (402 otherwise).