I am receiving 2 charges from Citizen One on my Am Exp bill for my iphone 11 Promax since 9/2019

I am getting 2 charges on my American Express for iPhone that if financed through Citizen One since 9/2019. I was told by Apple that I was getting charged for my old iPhone XS as well my new iPhone11 Promax. I thought I was doing the upgrade program when I bought new 11 online and hit the box that asked if I had a phone to buy back. I no longer have my XS and sent it back in Sept 2019. I did not realize I was getting 2 charges until 4/1/2020 and called and was on phone with Apple for 2hrs 40min and problem still not resolved. The Apple supervisor was not helpful and told me I had to pay over $200 to resolve issue! I should be getting a refund of the amount I have already paid and not having to pay more out of pocket! He told me that since it has been so long since this has been going on that I either had to pay out the remaining balance of my iPhone XS or turn in my current iPhone 11 and get $500 rebate but I would be without a phone and that is not acceptable because I am in healthcare in a hospital and need my phone for work. Not sure what to do and wish Apple stores were open so that I could resolve this!