A technique provides a phone call from a caller device operated by a human caller to an answerer device operated by a human answerer. The technique involves receiving a call request from the caller device. The call request includes a call button identifier which uniquely identifies a browser call button which is rendered on the caller device to the caller. The technique further involves identifying a source phone number based on the call button identifier. The technique further involves placing a call communication to the answerer device operated by the human answerer. The call communication indicates the source phone number as a source of the call communication. Accordingly, if the answerer device already has the context of associated with the source phone number already saved (e.g., in a contact list), the answerer device is able to automatically display that context in response to the call.