Product: Credit card or prepaid card

Capital One closed my credit card account. They did so without advance notice. The account was current with a balance of {$53.00}. The closure shows up on my credit report as account closed by credit grantor which caused a significant drop in my credit score. This drop is now affecting my ability to get a mortgage as well as the interest rate that I will potentially qualify for. So, there are real damages to their actions. 
It took me five calls and four days to get in contact with someone at capital one to discuss this. I originally learned about it from an alert sent by my credit score monitoring company that notified me of a status change for one of my accounts ( Cap One account now showed as " Closed by Credit Grantor '' ) and a 38-point decline in my credit score. At this point, I had not been notified by Capital One and I had no idea what was causing the closure of my account. After several days of contacting Cap One, trying to find out why. Each time being told that their customer service people had no information. And the only way I could find out anything was to leave a message with some obscure department that does not answer calls. It took four attempts to get connected and to leave a message. Four days later, I received a call from someone from their executive resolution team. XXXX ID # XXXX, spoke with me on a recorded line. And basically, told me nothing. The woman read from a letter which, by her own admission had not been sent to me yet. Amazing!! The letter stated something to the effect that management closed my account because they were not happy with my usage patterns. I don't use the card much. And I pay it off as soon as I do. Obviously, I am not a meaningful customer to them, because I do not generate interest charges or fees. Furthermore, when I asked the person who called me If I could speak to her manager or any person of authority at Capital One. She gave her managers name but would not give his ID number and said she would not allow me to speak with him. She told me that closing the account was within their rights as per the cardmember agreement. Repeating that statement as well as other jarred answers. Telling me there was no one else to speak with and she could be no further help. I then asked for who I could write to or call. She told me my only recourse was to write a letter and send it to the general correspondence PO box . I then asked who regulated them, which she did not initially know. She paused and had to investigate. She also was unable to direct me on how to contact their regulator and make a formal complaint. She later directed me the CFPB but did now know how to contact the bureau. 
The fact that they managed this process so poorly is not my primary concern. Although I think it should concern the CFPB. I don't need the account. My issue is that they could have simply given me the opportunity to close it on my own for a period of time, before doing so themselves. Or report it to the credit bureau in such a way that was not so damaging to my credit profile. I am no risk to them and there was no need to act so abruptly without notification or considering the effect of their actions