Complain channels with the client.

I was having a contract with this company for the past three years ,during the lapsing of the contract I called them to cancel my contract . Unfortunately they convince me to degrade my cover I did so and sign a new contract with them. In January 2024/01/23 they debited the past contract money plus the new one , On the 25th January 24 they went back to my account and debit the money unfortunately I was having no money in my account . I gave the call and they told me that they see on their system that I was over debited since on the 31st January 24 they debited on my account, I called them again and they told me that their system shows that I was over debited then I asked them about the bank charges the bank charged me for the insufficient fund that happened on the 25th January 24 who will be responsible for me to get my money back. I even asked them the channels to complain do they have or transfer my call to manager or somebody above her. She answered they don't have such channels. For me this is unfair.