This page describes the Telephony simulator and "ZZ" country code.
The Telephony Simulator is a tool that enables you to test Telephony SDK integration without the dependency of provisioning real phone numbers and sending text messages across the wire.
The "ZZ" Country Code
The "ZZ" country code is included in the list of supported countries for phone provisioning in projects that are in sandbox mode. Provisioning phone numbers in this region does not incur any number provisioning costs, as the resulting numbers are "simulated" and cannot communicate with other phone numbers.
Outgoing SMS and MMS messages from simulated numbers will by default be marked as successfully delivered. However, this behavior can be changed by sending a message to a test number as described below.
There are a few phone numbers that have special behavior in the simulated telephony region. These test numbers can be used to exercise specific code paths that may be difficult to test otherwise.
Note: The special behavior for these test numbers only occurs when using a phone number provisioned in the simulated telephony region.
Attempting to provision this phone number with the simulated telephony region will always fail.