Searches the phone numbers that are available to assign, in the country of the user's office. Search by area code, city or the first digits of a number, and page through the results with the cursor. The search has these fallbacks:

• A toll-free search with no matches returns any available toll-free numbers instead.
• For a US search that has run out of results, the response lists overlaying_area_codes: other area codes that serve the same region, to search next.
• When nothing matches an international search, set country_fallback to get numbers from the whole country instead; the response then has search_extended_to_country set.

Requires a user API key.

Rate limit: 1200 per minute.