icici bank - Extra Charges imposed by ICICI Bank

I have reedeemed the ICICI bank credit card reward points on **th of July **** during when the rewards points were managed by Payback vendor. Hence, I have redeemed my available points for two categories of vouchers viz *. Croma vouchers and *. Amazon Vouchers. The redemption was successful. But after * months I have received * charges that belong to reward redemption handling category. When I enquired the bank I was informed that one charge (**+GST) is for redemption of points against croma voucher and other (**+GST) is for redemption against amazon voucher. But there is no clarity for third charge of **+GST. When I called the customer care team I was asked to contact Payback team which does not make any sense. I would like to ask ICICI

*. Clarity and reason for the third charge which has no relevance
*. I was never informed about the underlying charges for redemption either in Payback or ICICI website / Mobile App
*. Charges are posed after * months
*. Redemption catalogue was not having vouchers of all denominations due to which customer was forced to select multiple categories