ICICI Bank — Mark up charges by ICICI Credit card for purchase in overseas

I have swiped an ICICI credit card for travel purposes, however recently I came to know that there is a. MARKUP deduction from my account. There was no prior intimation from the bank, nor an email.
Without informing how could you proceed with the deduction???
Was there any agreement or any contract signed by me???
Why don't the banks intimate the customers while opening the account, especially with international transactions????

Would request you to please intimate or send messages or WhatsApp to all those customers who are using your card internationally.
Till date you have deducted INR.12000 from my account.

o information on how much you are charging??
Where are the RBI guidelines mentioned in regard to the extra charges????

Waiting for your reply and also the refund from the bank with immediate effect.

I am going to raise complaint with RBI Banking Ombudsman