Identifying the caller
When an agent receives a call, the telephony system can use the caller's phone number to search for the caller in Zendesk Sell. If a user exists with the caller's number, the system can link the call to the existing contact or lead in Sell. If a contact or lead doesn't exist, it can create one for the caller. See Creating a contact or lead in Sell for a caller.
To look for a contact or lead in Sell, use the getResourcesByPhone endpoint with the caller's phone number:
client.invoke('getResourcesByPhone', phoneNumber);