ICICI Bank — Levied late fee for credit card

Address:

Nashik, Maharashtra, 422001

Respected sirs,
I am a frequent credit card user since the past 15 yrs. I had dropped my last payment cheque no. 00650 of icici bank in icici drop box much before the due dt i. E 11/5/2017 for amt 20000.
In my new statement there are four entries
12/05/17 chq received amt 2000 ref. 00650
15/05/17 chq received amt 20000 ref. 00650
15/05/17 chq reversed amt 2000 ref. 00650
15/05/17 late payment fee amt 750
I fail to understand why am i charged late pym fee for the error being occurred by the bank.
And on complaining to customer care i got this reply:
Dear ms. Chadha,
Thank you for writing to us.

We understand that you need a reversal of the below mentioned charges on your icici bank credit card xx4000.
[protected] late payment fee - db 750
[protected] service tax - db 112.50
However, based on the bank's policy, we regret to inform you that we are unable to reverse the charges levied on your credit card.
We request you to pay the outstanding amount to avoid the levy of further financial charges on your credit card.
Sincerely,

Manisha gairola
Customer service officer
Icici bank limited