Product: Debt collection

I recently found that medical debt that I had been approved temporary deferral of payments for by my medical provider was sent to a collections agency due to internal miscommunications by my medical provider. As such I reached out today, XX/XX/XXXX, to the debt collection agency, UCSB America, to establish a payment plan for the original amount due which was a little under {$1200.00}. On top of the original amount due there was an interest charge of over {$100.00}, which brought the total closer to {$1300.00}. 

I spoke with a representative to discuss a payment plan and inquire about the interest charge. They informed me that the interest was a 10 % annual interest charge by my medical provider backdating to the original service dates roughly one year ago, rather than interest from the collection agency themselves, which is why it came out to over {$100.00}. This sounded odd to me as the medical provider explicitly told me in the past there was no interest being charged on my payment plan. I called my medical provider to confirm this and they confirmed that they forwarded the collection to the debt collection agency at the original amount due for the services rendered which was the amount totaling to just under {$1200.00}, and did not include any additional interest charges. 

I then called UCSB America back to inquire about the interest again, a different representative answered saying that my representative was unavailable to talk and that I could call back at a later time. I said I was fine with continuing to speak to the representative I was already speaking with, and went on to explain what I had been told with the original UCSB representative, and how it did not coincide with what my medical provider was telling me. This new representative corrected what the original representative told me, indicating the interest charge was by UCSB America. I asked what the annual interest rate they were charging me was, they said it was 10 %. I explained there is no way to have over {$100.00} interest accrue on a balance of less than {$1200.00} between the date they received the debt ( XX/XX/XXXX ) and the date they billed me for it ( XX/XX/XXXX ), if the annual rate is 10 %. This requires an effective annual rate of over 500 % compounded continuously. As of now the balance has gone up another {$12.00} since the date of billing, which is still an approximate 120 % effective annual interest rate. I explained to the representative how these rates did not add up with the interest amount charged. The representative told me that he will have my original representative call me back by the end of the business day to resolve this issue, and hung up. I did not receive any call by the end of the business day by anyone from UCSB America. 

I have two issues with what has happened in my interactions thus far with UCSB America and its representatives. 

1. The first representative lied to me about where the interest was originating from, indicating that it was originating from my medical provider, rather than UCSB America themselves, and thereby falsely inflating the amount I had owed to my medical provider. 
2. The amount UCSB America is charging for interest is not the 10 % annual interest rate they are claiming it is, rather it is effectively 12 times higher at approximately 120 % annually as of now, and was over 500 % at the date of billing from them. 

Both of these are false claims intended to get me to pay more than what I owe, and I suspect they have succeeded in doing so to others who may not have questioned the claims they were making.