Product: Credit card or prepaid card

On XX/XX/2022, I received notification that my Gemini credit card statement was ready for the period XX/XX/2022 to XX/XX/2022. The payment due date was XX/XX/2022 in the amount of {$680.00}. I scheduled this payment from my XXXX XXXX XXXX to be sent on XX/XX/2022 and delivered on XX/XX/2022. The send date works backward from the desired delivery date. XXXX states that there was no issue processing the payment on their end and that the payment was delivered on time. Gemini, however, states that the payment was received on XX/XX/2022. Consequently, I was charged a {$20.00} late payment fee and {$11.00} of interest on my ensuing statement for the period XX/XX/2022 to XX/XX/2022. The interest charge was calculated on a balance of {$830.00} ( not the {$680.00} that they claim was XXXX day late and no reconciliation was provided ) at a rate of XXXX XXXX for what appears to be 31 days ( not the 1 day that they claim the payment was late ). I immediately disputed the fact with Gemini that the payment was XXXX day late and provided them with all of the supporting detail. They agreed to waive the {$20.00} late penalty fee but would not agree to waive the {$11.00} interest charge ( which I think is the most appropriate given the fact pattern ) OR lower it to XXXX day 's worth of interest despite several attempts on my part. 

Next month, the new balance on the statement for the period XX/XX/2022 to XX/XX/2022 was {$560.00}. This amount included both the {$20.00} late payment fee ( waived ) and the {$11.00} of interest ( disputed ) and was due XX/XX/2022. To avoid this same type of issue, I schedule my next payment much earlier and including the fee and interest amounts. This next payment from my XXXX checking account was sent on XX/XX/2022 and delivered on XX/XX/2022, 7 days in advance of the next payment due date. Per Gemini 's records, this payment was in fact received and processed on XX/XX/2022. Magically, there was no difference with XXXX 's records on the delivery date this time. That said, when I received my Gemini statement for the period XX/XX/2022 to XX/XX/2022, there was an additional interest charge of {$10.00}. This interest was calculated on a balance of {$720.00} ( no reconciliation provided ) at a rate of XXXX XXXX  for what appears to be 30 days. At this point, I called them yet again to dispute this second round of interest charges and asked how I could be getting charged more interest for a payment that was received 7 days early. I explained that the only acceptable resolution to me was if they refunded the total interest charges of {$21.00} ( {$11.00} from the first month and {$10.00} from the second month ) or otherwise I would file a complaint with the CFPB. There is no reasonable explanation for either XXXX ) the initial payment being posted 1 day late or XXXX ) the calculation of the interest charges ( both number of days and balance subject to charge ). They declined to refund my interest. I have since fully paid off the card and there is a XXXX XXXX XXXX - I do not want to use the card further until there is an acceptable resolution of this matter I'm happy to provide any and all further information in support of the above description. I am attaching the initial proof of payment from XXXX below. Please note that the check image shows that they cashed the check XXXXXXXX XXXX XXXX. My concern is that it was done purposefully ( posted/cashed XXXX XXXX XXXX despite earlier delivery ), since I have never ever had this issue with payment scheduling for any other credit card company. Thank you for your help in this matter.