Product: Checking or savings account

I have a customer of Capital One Bank for many years with no incident, I have maintained a checking account but on XX/XX/XXXX, when my available balance was {$3.00}, Capital One honored a payment of {$100.00}, which overdrew my account in the amount of {$100.00}. I immediately called Capital One and filed a dispute. I informed Capital One that I was disputing this amount not because of fraud but because this was a recurring charge but I cancelled the account because I wasn't using the service. They issued me a credit of the overdrawn balance. A few days later I received an email stating I needed to provide proof that I cancelled the account. Since I could not figure out how to prove a phone call, I made no further claim, since the amount was only {$100.00}. Capital One reversed the credit and added the balance back on my account, resulting in an overdraft. I made deposits to my account to cover charges to XXXX in the amount of {$320.00}. On XXXX XXXX, I made a payment to XXXX XXXX the amount of {$320.00}, but when I later checked my account balance, I was charged XXXX payments of {$320.00}, resulting in my account being overdrawn in the amount of {$250.00}. I received a text message asking me if I trying to make a payment of {$320.00}, to which I replied " yes '' and Capital One replied they would process the payment, but when I checked my account, I was charged for the XXXX payments. When I called Capital One, they told me they would open another claim, and they issued a temporary credit. I received an email saying they needed additional information, but before I could submit the info they asked for, they emailed me that the claim was denied. I returned the car to XXXX on XX/XX/XXXX but on XX/XX/XXXX, I was charged {$640.00}, which caused my account to in the negative in the amount XXXX. I was told by Capital One that I wouldn't receive until after the investigation. I received an email stating additional info was needed on XXXX, but on XXXX, they emailed me that the claim was denied, before I could even get the information in. 
On XX/XX/XXXX, my Social Security check was deposited in the amount of {$1100.00}, but because of the overages in my checking account, I was left with {$100.00} for the month. I am a senior citizen, on a fixed income so this has been devastating for me. I was XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXXut these additional charges has negatively impacted me. Capital One refuses to give me an acceptable explanation because in all my years, with Capital One as well as other banks, I have never heard of a bank paying charges that there is not sufficient funds available to pay these charges. I don't have overdraft protection and it is beyond ridiculous for I bank to continue to approve payments that are not backed up by funds available in the account. I have been asked to prove these charges weren't authorized by me, but my question is why would they pay transactions that leaves my account {$1000.00} in the negative. As I previously stated, I am on a fixed income and this situation has left me with no money in my account ( to which their response is it not our problem because these are charges I owe ). Meanwhile, I can't pay my rent, utilities, phone, internet, life insurance, etc. I receive XXXX social security retirement check monthly and I will be in this situation until XX/XX/XXXX. 
Thank you in advance for your attention to this matter.