When a user clicks a phone number in Upsales, the phone widget fires up and your app gets a request to the following endpoint
/call
The requests body.data contains the phone number to call as well as the id of the company, contact and some related data (if any).
"data": {
"number": "+1 555 8772537",
"clientId": 123,
"contactId": 345,
"related": {...}
}
Use this request to initiate the phone call.