Citibank Bank Account Or Service Complaint

Citibank Bank account or service department,

Cashing a check without an account Problems caused by my funds being low New York

I autopay my Citi credit card online and changed the bank account for them to withdraw the funds. I have an email confirming the new account change, yet the following month, Citi withdrew funds from my previous account, which no longer had any money in it, causing me huge fees and penalties! They refused to accept responsibility for their mistake and want me to pay those fees and penalties. I 've been trying to resolve this dispute for the past few weeks and they keep pointing the finger at my previous bank.