Do phone numbers really cost anything in the US? Or is there an upper limit to the length of a phone number? Otherwise, they can just allocate a million which would be enough to have a grace period of at least a year until phone numbers would be reused.
All phone numbers in the US (actually, North America and some Caribbean islands) are the form AAA-XXX-YYYY, and there's a finite number of AAA (or area codes) that have been issued so far. And some types of numbers are not possible, mostly for historic reasons. I'm not sure how much a block of numbers actually cost in the US, but they're not free. I know a company I worked for tried hard to compress the range of numbers they had so they could give back part of an exchange to save money.