Harassment by American Express Bank

I had an American Express Card which was given to me free of cost for 1 year by American Express in July 2020. After 1 year before the expiry of the 1st year. I had informed American Express to discontinue the card. All the card liabilities were paid. American Express did not close the card & charged me annual fees of Rs 60000 + 18% GST. I had stopped using the card completely. But now they are harassing me to recover the amount. The total amount outstanding is Rs 82000. I had written to them also in November 2022. But the harassment has continued. In February 2023, they sent me a legal notice threatening to file a case to which I had replied asking them to furnish the transactions which I had done on the card but not paid. After that there were no communication from them but they are sending me text messages & WhatsApp messages. Sometimes I get a call demanding money. Everytime it is a different person who talks to me & I have to explain this history all over again.Till now I must have spoken to 25-30 different people who are pestering me. Please help.