BACK or BAK ?

Suatu hari di flight Rome.........

Passenger : Excuse me, can I have water?
Kumbang : Certainly madam, I'll come back later
Passenger : Sorry??
Kumbang : I'll come back (baca : bek)
Passenger : What??
Kumbang : I'll be BACK (baca : bek)
Passenger : *masih ngga ngerti juga* Haa???
Kumbang : *frustasi* I'll be BAK madam
Passenger : Ohh.. ok
Kumbang : *ngabur ke toilet sambil ngakak*