Product: Credit card

I received a call in XXXX telling me my XXXX XXXX XXXX payment was overdue and asking me to pay over the phone. I thought this was a scam call as I always pay my bills in full and on time. I hung up and called the phone number on the back of my XXXX XXXX. To my surprise it was overdue and I never received a statement in the mail. I assumed it was lost in the mail and paid my bill in full using the online app for my credit union. I then started to receive calls that my XXXX credit card payment was overdue for the same month, I also did not receive a bill in the mail for XXXX. I soon discovered both of these stores use Comenity Bank. This is very suspicious that the only two bills I didnt receive were both from the same organization. I also paid this bill in full through my credit unions online app. I thought the issue was over until I received my billing statements in XXXX. XXXX had applied my payment of {$500.00} on XX/XX/2023 and then removed this payment on XX/XX/2023. So, they charged me {$500.00} plus interest. I called XXXX who put in a request to investigate what happened. My XXXX statement also had an issue. First, with all of the phone calls, I double paid them. Once with interest and late fees ( {$130.00} ) and once without the interest and late fees ( {$100.00} ). The statement said I was late with my payment and consequently I was charged {$66.00} in late fees. I did not understand this because I paid the bill in full on my banking app several days before my paper bill came in the mail. When I called Comenity Bank they said this was my error in not getting my payment to them on time. I contacted my credit union who confirmed my checks to Comenity Bank were dated XX/XX/2023 and the XXXX tracking showed my checks arrived at Comenity Bank in XXXX Texas on XX/XX/2023. Yet, Comenity Bank did not process my payments until XX/XX/2023 resulting in the {$66.00} late fees. I called Comenity Bank back and explained the documentation I had from my credit union. They still refused to refund my money. I asked to speak with a supervisor. It took several attempts before they agreed to connect me. I heard the call picked up and then hung up disconnecting my call. I have also reached out to XXXX through email and phone. The customer service representatives are very nice and say they are expediting my concerns to a manager and I will hear back in 48 hours. I have still not heard back and this was over one week ago. I am asking for your help to get my {$66.00} back from XXXX. I also want to bring attention and hopefully an investigation of Comenity Banks unethical behavior. I believe their actions are purposefully dishonest with the goal of charging erroneous late fees and interest. When I spoke to the representative at my credit union she informed me Comenity Bank did something similar to her. When I asked what she did about it, she said nothing, she figured it would be a waste of her time and just paid them. This led me to wonder, how many people are Comenity Bank doing this to? This is not right and I am taking the time to tell someone about it. I hope you can help. I attached the credit card statements for XXXX from both XXXX and XXXX as well as the documentation from my bank showing the check dates and XXXX tracking information.