ICICI Bank — Bank refuses to register my complaint

I have icici bank credit card ending 9005.
i use icici i mobile pay app to pay total outstanding amount.
before due date of payment, i checked the total outstanding amount due on i mobile pay app, it was 0.
so i havent made payment.
now the bank charged me rs 885 for late fees.
now bank refuses to register the complaint.
custumer care says the bill amount was rs 17490, & it was reversed back on 15 june. the payment due date was 29 june.
thats why on i mobile app it showed total outstanding amount 0.
but they said i have to pay the bill.
now bank refuses to refund or register complaint.
very bad experince.
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