Isn't the issue that you WANT them to charge you in USD, at the USD rate you reserved? Or was the underlying reservation in INR?
If the former what is happening is you are reserving at a USD rate, they use some sort of 'tourism' rate to convert to INR, charge you in INR then your credit card converts it back to USD at the different spot rate which result in a USD charge higher than your reservation. Nothing to do with DCC in that case.