Product: Credit card

A promotional purchase was applied to a transaction on my Care Credit card for a medical service in the amount of {$1700.00}. I set my auto-pay accordingly to ensure that the amount paid monthly would pay the promotional purchase within the XXXX term that I chose. I had other transactions after that one were I added amounts necessary to satisfy those payments, and I would adjust accordingly as I would pay them off. However, the credit card company allocated my monthly payments at their discretion which caused a balance of {$500.00} due on the original promotional purchase, which I was unaware of because I set the card on auto-pay thinking I was covered. It was a complete shock to me when I checked on the card to update my XXXX budget and the balance due was higher than what it was in XXXX reconciliations. I called the company several times to try to understand the issue, to which I got no answers, until I combed through statements and realized the company applied a {$700.00} interest charge to my account due to not paying off the balance of {$500.00}! Keeping in mind that I had paid already over {$1200.00} of the original purchase, and my monthly payments set where more that double the minimum due, and only {$150.00} less than the {$500.00} needed to avoid the interest! I have never missed a payment and never had interest charges on previous purchases, so I requested that they remove the interest and I would pay the promo purchase in full - they refused. I requested the allocation schedule for transparency on how my payments were being applied to the promotions- they refused. I asked what the percentage for allocations of payments on promotional purchases was- they refused. I asked for proof of alerts, emails, notifications that would have indicated that I had a {$500.00} balance to pay or I would incur a {$700.00} interest charge - they said I received my statements, however, the statements do no clearly outline the penalty. All they say is that a promotional purchase is due. Not to mention I have the payments on auto-pay with a paperless billing account so all I get is a reminder that I have a statement - no specific indication of promotional purchases ending or interest penalties being applied that would alert me to take further action. When I tried to disable the auto-pay there was no way to do that myself through the portal, I had to call the customer service line and demand that they disable it. Yet the ONLY way you can ensure that your payments apply accordingly to the promotional purchases is to call the customer service line and manually calculate the amount then perform separate transactions to apply accordingly- and I think there is a service charge for this type of payment!!! This company is predatory- they trained my medical service provider to encourage me to use the card because of the 0 % interest rate. They never indicated that the interest was accruing on the back end let alone that I would have to manually configure the payments and call monthly to apply allocation of those payments in order to avoid the interest penalty. This is predatory, fraudulent, lacks transparency, and is wrought with fraud as they hire third party service centers who actually had chickens cooing in the background of the call and when I asked to escalate the call they then transferred me to their " supervisor '' who had the exact same background noise. All in an effort to exhaust me into submission, continually telling me there was no option and no other way to dispute the charges. If I was elderly or learning disabled ( not uncommon for medical services ) then I would be at a complete disadvantage and they know it! This is unlawful.