This might be related to the fact that there are some restrictions for India ,the INR currency (only for local payments) and the USD (or any other) currency (international Payments only)
Just to clarify, USD transaction is not allowed between Indian buyer and Indian seller account. In order to receive payments from Indian buyers, it should be in INR, but you can receive USD payments from other countries.
Please note that Indian domestic payment must be exclusively made in INR currency. INR currency can only be process by Indian domestic payment only. International customer who tried to make payment to an Indian merchant need to process the payment in currency other than INR (example USD).
For International Payments -> USD currency For Local Payments -> INR currency.
So, if the merchant/seller is from India and the buyer is from India as well (as this is the case), you can only pay in INR. The merchant must offer another option for you to pay in INR.