Credit card closure from citi

Looking for help. I am in India and I bought cryptocurrency from UK exchange in July 2017 using CITIBANK credit card. CITI payment gateway allowed the transaction and it was successful. Then on January 2018 ( after six months), suddenly CITI foreclosed my creditcard permanently mentioning that as you did a transaction which is not allowed under FEMA. After that CITI people are after me to clear the dues/payments (INR 72k), i'm keep on requesting to CITI, issue me a new card and transfer the balance that need to be paid, and i will do the payment. But now they are keep on charging the interest to me and calling again and again from collection department. My point is, why citi payment gateway passed that transaction, (why it didnt allowed while doing a transaction) and reissue me a new card and do the balance transfer so that i will pay that. Kindly suggest me. // Reason in EMAIL "We hereby wish to inform you that an Indian resident is permitted to make only those foreign exchange transactions on a credit card that are permissible under the Foreign Exchange Management Act (FEMA) 1999. Remittance in any form towards overseas exchange trading through internet /electronic trading portals is not permitted under the foreign Exchange Management Act (FEMA), 1999. Indian residents are also prohibited from trading in foreign exchange, including trading on binary options in US dollars where the underlying assets may be bitcoins, stocks, commodities etc in domestic and overseas market. We wish to draw your attention to clause 6.2, 7.5 and 33.2(K) of the card member Terms and Conditions"