I had paid the debt in full that I owed to the health care provider XXXX last year via their ebillpay system. I was surprised when I got a call from the collection agency this year. After their call I faxed them the proof of payment to the collection agency. 

Recently, I received another letter asking for the same payment which did n't include my payment in the transaction history that was provided to me. 

I am being harassed by these letters and the collection agency is not doing it 's due diligence to investigate.