Perhaps something like this;
case when CALL_TYPE = 2 AND CLFAG2 !=IN ('I','i','n') then
(RING_TIME + QUEUE_TIME + DELAY_TIME + CTYPE_TIME +HOLD_TIME + TALK_TIME)
when
CALL_TYPE =IN(15,17)) then
(RING_TIME + QUEUE_TIME + DELAY_TIME + CTYPE_TIME +HOLD_TIME + TALK_TIME)
else 0 END AS TOTALTIME