CLOSING OF CREDIT CARD ACCOUNT

My husband closed his credit card account on 20/12/2020. On January 2121 received an account with costs added to the account. I contact them and explained that the account was closed. Their answer was that there were an insurence polisy that was not cancelled and I must do it before the account can be closed. In February 2021 I received another statement with more costs added. I phone their all center and they said that there were never been a request for closing of the account. Again I sent an email with proof of insurence cancellation but now they ignore me. I am at my wits end what to do now to get the account closed.