Mail Kotak and ask clarification why it has not been closed yet, ask them to close it immediately, they may ask you to send CIBIL Unlocked Report with Control Number.
L1:
kotakmahindrabank.creditcards@kotak.com
L2, Mr P. Balgi Nodal Desk:
p.balgi@kotakbank.com
L3, Mr. K. Vora,Principal Nodal Desk:
k.vora@kotakbank.com
k.vora2@kotak.com
Hope, I am able to answer your query, mark my comment as solution.