Product: Credit card or prepaid card

In XX/XX/XXXX, I obtained an American Express " Blue Cash Everyday '' credit card with a 15 month introductory 0 % APR interest rate for balance transfers and all purchases. I transferred a balance of {$3700.00} from another card, which went through on XX/XX/XXXX. I also used the card to make one purchase on XX/XX/XXXX for {$87.00}. 

When I received my first billing statement, I was dismayed to see I was being charged {$36.00} in interest for allegedly {$1800.00} in purchases under " Balance Subject to Interest Rate '' " Purchases '' in the " Interest Charge Calculation '' section on the billing statement. My balance transfer of was also erroneously listed in that section under " Balance Subject to Interest Rate '' as {$56.00}, instead of the actual amount of {$3700.00}. These numbers are erroneous in numerous ways : they don't add up with the purchase I made ( there are not {$1800.00} in purchases itemized on the statement, only the one for {$87.00} ), none  of my purchases should be charged interest until after the introductory period is up on XX/XX/XXXX, and the incorrect balance transfer amount listed in the " Interest Charge Calculation '' section. These are random amounts without any reason behind them. 

I contacted American Express ' customer service after viewing this statement, to ask why I was being charged interest during the introductory rate period and the random amounts listed on my statement. I was told this was definitely a billing mistake on their end, and they would fix it. I felt this would get taken care of and would be reversed on my next billing statement. 

I then viewed the XX/XX/XXXX billing statement, where not only was nothing fixed or reversed, but I was being charged {$98.00} in interest for " Purchases '' of {$3800.00}. My statement lists {$390.00} in itemized purchases during that period. The balance transfer amount is now listed as {$110.00}, and my " Introductory Purchase '' amount is {$110.00}. Again, completely random amounts that don't make sense. I called their customer service line once again, and was told they were " aware of the issue '' with my account, and my account was " heavily notated '', and they were " working on it ''. Feeling less optimistic about a resolution, I decided to stop using my AmEx card for any more purchases. 

Now, after viewing my XX/XX/XXXX billing statement, I see once again nothing has been fixed or credited to my account ( assuming my payments are going first towards the erroneously charged interest instead of the principal ), and I'm still being charged interest for " purchase '' amounts I did not make, which is {$83.00} for allegedly {$3800.00} in purchases not itemized on the statement. I have decided to take the step of filing a complaint with the CFPB at this point, because I feel the company has had plenty of time to fix this issue going back to XX/XX/XXXX, and doesn't care they are committing consumer fraud by refusing to fix their billing issues. 

In summary, I have been charged {$130.00} in interest from XX/XX/XXXX, and {$83.00} so far in XX/XX/XXXX, for a total of {$210.00} I should not have been charged per the 0 % interest for 15 months agreement I signed up for.