Returns a single phone number available for purchase, whether it is already in inventory or can be acquired for you. Numbers supplied through a carrier remain available only while the carrier has them, so a number listed a moment ago may already be gone. A `404` means the number is currently unavailable for sale. Phone number in E.164 format. The leading `+` is optional. Phone number in E.164 format. ISO 3166-1 alpha-2 country code. Physical type of this phone number. Channel capabilities supported by this number.