FS originates call to carrier. FS receives "200 OK" from carrier and send ACK but for some reasons ACK not received by carrier.

Then carrier retransmits "200 OK" messages and all retransmits also will failed.

Carrier send BYE message after timeout as call not established correctly.

Is possible to get event of failed call on FS side. As example - we got several "200 OK" messages and "BYE" message is received after 10 sec of last "20 OK"?