I think you didnt get the fact here. If 4 berths quota, and if they were to cancel, its his group itself who has got those 4 berths. That means you are suggesting his own group members to cancel their tickets to enable his WL group members to get confirmed berths :-) One suggestion I gave was to book using Senior citizen quota if at all they are travelling (Male >= 60, Female >=45, 1 passenger per PNR). Other option is if berths are available till last station of the train (Guwahati), then book till Guwahati and get down at Jalpaiguri.