A hang up cause is a variable sent to your callBack URL or Events URL or both when an outbound call via API is sent and not answered.
Below are the parameters to expect:
UNSPECIFIED: This cause happens on very rare occasions when a valid hangup cause can’t be obtained. We (AT) are usually alerted for this and we look into it immediately.
NORMAL_CLEARING: This cause indicates that the call is being cleared because one of the users involved in the call has requested that the call be cleared. This also means the call was successfully answered and successfully ended.
CALL_REJECTED: This cause indicates the called party does not wish to accept this call.
NORMAL_TEMPORARY_FAILURE: This cause indicates that the network is not functioning correctly and that the condition is not likely to last a long period of time. The user may wish to try another call attempt almost immediately.
RECOVERY_ON_TIMER_EXPIRE: This cause indicates the expiration of a request, to the called party. This is often associated with NAT problems. It affects mostly softphones with SIP numbers.
ORIGINATOR_CANCEL: The caller initiated a call and then hang up before the recipient picked up. This normally happens when using the Dial call action.
LOSE_RACE: This occurs when a call is initiated to multiple phone numbers. Once one recipient picks up, the others will have a LOSE_RACE hangup cause. You can get this when using the Dial call action.
USER_BUSY: This cause is used to indicate that the called party is unable to accept another call because the user busy condition has been encountered/engaged on another call.
NO_ANSWER: This cause is used when the called party has been alerted but does not respond with a connect indication within a prescribed period of time.
NO_USER_RESPONSE: This cause is used when a called party does not respond to a call establishment message with either an alerting or connect indication within the prescribed period of time allocated.
SUBSCRIBER_ABSENT: This cause value is used when a mobile station has logged off, radio contact is not obtained with a mobile station or if a personal telecommunication user is temporarily not addressable at any user-network interface.
SERVICE_UNAVAILABLE: This cause is used to report a service not available.
USER_NOT_REGISTERED: This means you tried to originate a call to a SIP user who forgot to register/hasn't registered.
UNALLOCATED_NUMBER: This cause indicates that the called party cannot be reached because, although the called party number is in a valid format, it is not currently allocated (assigned).
Want to also know about Call Transition states that are posted to your Callback and Events URL? Click here