Product: Credit card or prepaid card

I had an authorized user on my Capital one account whom I allowed to use the card to rent a car ( monthly lease ) from XXXX XXXX XXXX XXXX. The lease began in XX/XX/XXXX. The agreed amount was XXXX per month. The monthly amount was paid by capital one and the authorized user paid the billed amount each month. The first bill XX/XX/XXXX, and the account was then billed every 30 days. This went on from XX/XX/XXXX until XX/XX/XXXX. The authorized user had a problem with receiving his pay check from his employer in XX/XX/XXXX which caused him to go a month behind. Capital one began to send me emails to notify me that XXXX XXXX XXXX XXXX was trying to charge the account for {$800.00} to pay the XX/XX/XXXX bill. There was not enough credit on the account to cover the charge. The notices from Capital one suggested that I either pay the account to have enough credit available or to increase the credit limit. I called capital one several time to request a credit line increase which I was denied because I had an increase less than 6 months prior. XXXX XXXX continue to bill the account for {$800.00} to cover the XX/XX/XXXX bill and I continue to receive the emails from Capital one suggesting that I make a payment or increase the credit line. The authorize user was contacted by XXXX XXXX stating that if he could not make the XX/XX/XXXX payment he would need to return the car. He made many attempts to get his pay from his employer and to secure enough funds to pay the XX/XX/XXXX bill from XXXX XXXX. On XX/XX/XXXX XXXX returned the vehicle to XXXX XXXX. That day I received notice that charges were being made to my account. I called Capital one to determine where and why the charges were being made in such weird amounts from XXXX XXXX. The Capital one representative explained that the amounts varied and she could not determine why they were coming in like that at one time ( varying in amounts on the same day ) so she decided to do a three way call to XXXX XXXX to determine why the account was being charged. The XXXX representative stated that the computer was trying to get the payments from the account and it ( computer system ) was designed to charge various amounts in order to get payment. I explained that appeared to be suspicious and unethical. She became belligerent and told me that the a charges should be more than the $ 800 monthly charge because he did not pay. I explained that was not possible as the monthly lease was for {$800.00} a month. I explained the only bill that was not paid was for XX/XX/XXXX. The representative stated she would refer the account to their collection department and I would hear from them. After the call ended the Capital one representative stated she would place a block on the account to stop further charges. Two days later my account which had a limit of {$1700.00} ( only {$90.00} was available at the time ) was then charged for {$2400.00}. That charge took my account for the limit by {$2400.00}. I called capital one and their explanation was that there was no detailed record of my call on XX/XX/XXXX. I asked it that call was recorded and they told me that they would have to pull the recording. I made a request to dispute the charge and requested that they pull the recording because the {$2400.00} charge should not have gone through on a blocked account and on and account that only had {$90.00} available. I had been denied a credit increase many times. Their answer was that they allowed the overdraft as a courtesy. I asked how can you allow {$2400.00} but not allow {$800.00}. The only answer was that the computer makes the determination. I am very frustrated that we never received a notification from XXXX XXXX XXXX as to how we were being charged for {$2400.00} but the account was being billed for {$800.00} up to the very moment he return the vehicle. Also Capital one did not protect me as a customer by allowing the charged that I did not have available credit for. The charge should have been rejected for {$2400.00} as it was rejected of {$800.00}. I paid very little interest on my capital one account because the bill was paid in full most often. it appears the bank made a decision that would benefit them and not in the best interest of the consumer. I did what I needed to do to protect my account from additional charges when I agreed to have the account blocked. I do not feel that my right to be informed was protected and i believe it is an unfair business practice to allow an account to be overcharged by {$2400.00}. Which will reflect as a credit risk to the credit bureaus for a bill that I was never notified of until it was already charged to my account. I have a right to fair due process.