What is a zone?

Elastic SIP Trunking calls to US and Canadian destinations are billed by zone. Each zone represents a collection of area codes and prefixes (NPA-NXX) where we charge the same rate. By segmenting destinations into zones, we are able to offer more competitive rates for each zone.

How do I tell which zone my call will fall under?

The vast majority of calls should fall into Zone 1. Well over 90% of Twilio’s overall calls are Zone 1. A specific list of prefixes and zones is available in the downloadable CSV rate deck at  https://www.twilio.com/pricing/csv/sip-trunking-termination.