fe7c9e08_oice__VoIP__and_Text_Messaging__Description
[Property] RequestUrl [Description] 
The URL of the resource that generated the notification. If the notification was generated during a phone call: This is the URL of the resource on YOUR SERVER that caused the notification. If the notification was generated by your use of the REST API: This is the URL of the REST resource you were attempting to request on Twilio's servers.
Twilio Cloud Communications - APIs for Voice, VoIP, and Text Messaging