The Vonage Business Cloud Extension API enables you to retrieve information about extensions. Your application must subscribe to the Provisioning API suite to use this API.
curl \
-H "Authorization: Bearer $API_KEY" \
https://api.vonage.com/t/vbc.prod/provisioning/api/accounts/{account_id}/extensionscurl \
-H "Authorization: Bearer $API_KEY" \
https://api.vonage.com/t/vbc.prod/provisioning/api/accounts/{account_id}/extensions/{extension_number}