Following are the possible status in call logs:
Accepted, Connected, line Busy, Not Answered, No Answer, Hang Up, Stopped, Internal Error, No Credit, Restricted Number, Wrong Number, International Disabled, International Restricted, Bad Number, Info 411 Restricted, Customer 611 Restricted, No Digital Line, Failed Try Again, Max Call Limit, Too Many Calls, Calls Not Accepted, Number Not Allowed, Number Blocked, Number Disabled, Resource Error, Call Loop, Fax Not Received, Fax Partially Sent, Fax Not Sent, Fax Poor Line, Fax Prepare Error, Fax Save Error, Fax Send Error
refer: https://developers.ringcentral.com/api-reference/Call-Log/readUserCallRecord
Carrier tries to deliver within 48 hours or so and then expires the message for showing delivery failed
