Product: Credit card

I am writing to formally lodge a complaint against American Express regarding their unfair and predatory practices concerning my business credit card account. 
In XX/XX/year>, I was issued a business credit card from American Express, which was marketed as offering 0 % APR for the first XXXX  months. However, after a few months of use, I encountered an issue that I believe is not only unfair but also predatory in nature. 
For a period of XXXX months, American Express XXXX XXXX to exceed the credit limit on my card without any immediate consequences or notifications indicating that I was doing so. Based on this lack of response from American Express, I reasonably assumed that additional charges beyond the credit limit were permissible, and that the card would decline transactions if the limit was reached. 
To my surprise and detriment, American Express subsequently increased my APR to approximately 20 %, with the rationale that I had spent over the credit limit. This abrupt increase in APR, without prior notice or a warning that I was exceeding the limit, feels deceptive and is causing me significant financial harm. 
It is my understanding that if a credit card 's limit is reached, additional charges should not be processed. Instead, American Express not only allowed these charges but also retroactively penalized me for actions that they implicitly permitted. I believe this is a clear violation of fair lending practices and request that the CFPB investigate this matter. 
Justification for Complaint : Implicit Permission to Exceed Credit Limit : By allowing me to exceed my credit limit repeatedly without notifying me or declining transactions, American Express may have created a reasonable expectation that these actions were permitted without consequences. The sudden penalty in the form of a higher APR could be seen as unfair and deceptive. 
Lack of Communication : Credit card companies are generally expected to notify cardholders if they exceed their credit limits or if any actions could lead to significant changes in the terms of their account, such as an increase in APR. If American Express did not provide such notifications, this could be a violation of fair lending practices. 
Predatory Nature of the XXXX Increase : The sudden increase in XXXX to 20 % after the initial 0 % promotional period, particularly if it was triggered by actions implicitly permitted by American Express, could be viewed as predatory. This is especially true if the increase imposes a significant financial burden on me. 
Comparable Experience with Other Lenders : I currently have XXXX other credit cards with major lenders, including Capital XXXX, Bank XXXX XXXX, and XXXX. Additionally, I have had accounts with XXXX and XXXX, which were closed due to intentional inactivity. In my experience with these other lenders, I have never encountered an issue of this nature. The practices Ive encountered with American Express are both unprecedented and deeply concerning. 
Given these factors, I believe that filing this complaint with the CFPB is justified. The CFPBs role in protecting consumers from unfair and abusive financial practices is crucial, and I hope that this complaint will not only help resolve my issue but also bring attention to practices that might be affecting other consumers as well. 
Thank you for your attention to this matter. I look forward to your prompt response and any assistance you can provide in resolving this issue.