Citibank — refusal to close credit cards

I received a credit card statement saying, where they made a demand for paying 1147 for some charges. It's free for life card. This is unacceptable. There was no pending bills to be cleared. Never spend on my card for more than 6 months and nothing is due. And still getting statements asking to clear dues.
So i asked them to close the cards. (Two cards where there). But they refuse to close. Citibank has no system to address consumer grievances.
After that, i paid the amount that i never spent. Still refusing to close the account.
Regards
Anita joseph