Debt removal

I decided to join NDA in 2019 uponreceiving a call from them selling me their products.upon our discussion I decided that they should place me under debt review due to my credit card only but the car I will continue financing it since it was not a problem.however they went about to contact VW dealership and they negotiated to mark down the instalment I was paying,and then I received a call from my dealership telling me that they won’t allow this and I should not involve them in any dealing with NDA.I then went back to contact NDA informing them that I no longer want their service and they should cancel me from their contract.Now that I have recently finished paying off the credit card that was part of the contract I told them they should give me a clearance and remove me from their system.With that communication being said they sent me a invoice that upon receipt of the clearance I must settle it,which I did.But surprisingly now they are telling me to produce a paid up letter for my car which was not part of the deal and they are refusing to send me the electronic conversation that was exchanged between me and them.