According to the https://www.twilio.com/docs/voice/twiml#request-parameters ParentCallSid param can be sent in the VoiceRequest. I believe it's important to have it there, because the StatusCallbackRequest which inherits that request always contains it.
`
/// < summary >
/// A unique identifier for the call that created this leg. This parameter is not passed if this is the first leg of a call.
/// </ summary >
According to the https://www.twilio.com/docs/voice/twiml#request-parameters ParentCallSid param can be sent in the VoiceRequest. I believe it's important to have it there, because the StatusCallbackRequest which inherits that request always contains it.
`
/// < summary > /// A unique identifier for the call that created this leg. This parameter is not passed if this is the first leg of a call. /// </ summary >
`