On XXXX XXXX I got a letter from Nation Star Mortgage stating that my mortgage loan was transferred to them on XXXX XXXX. Stating as of XXXX XXXX, XXXX they are my new lenders. It also included a bill of XXXX with the due date of XXXX/XXXX/XXXX. However, I already sent my XXXX and my XXXX payments to XXXX ( the previous lender ). XXXX payment was sent on XXXX/XXXX/XXXX check # XXXX XXXX} it was taken out by XXXX on XXXX/XXXX/XXXX. XXXX payment was sent XXXX/XXXX/XXXX check # XXXX XXXX it was taken out on XXXX/XXXX/XXXX. I contacted Nation Star and talked to a representative names XXXX. She did not help me at all she told me to call XXXX. I called XXXX but because my case was transferred I could not speak to a human representative and the automated system gave me a phone number to contact Nation Star. My second call to Nation Star I spoke with XXXX, and she was telling me the same thing to call XXXX. I had to argue with her to three-way the conversation because I could not get a hold of anyone. She three-wayed the conversation with XXXX and XXXX said it was XXXX to Nation Star and the transaction number is : XXXX. In between this, I got another statement from Nation Star and the billing amount was XXXX. on XXXX/XXXX/XXXX I made a third phone call and spoke with XXXX, she three-wayed with XXXX again and XXXX picked up again and repeated that the second XXXX payment was XXXX to them too. XXXX told me she does n't see the second paycheck and she was going to send a note to the research department to start an investigation and they were going to notify me with the results in 7 to 10 business days. I asked her if they need any additional documentations from me for example copy of checks and banks statements. She said no everything is fine, and I did the XXXX payment over the phone with XXXX for XXXX. I never received any notification from them. I called back on XXXX/XXXX/XXXX and spoke with XXXX. XXXX said the previous investigation was dropped because I did not provide any documentation. This is what angered me further and I requested to speak with the supervisor and she said no one is available and she will try to help me. XXXX Three-wayed with my XXXX bank and the XXXX representative XXXX told me to just send the pdf formats of my bank statements. XXXX gave me her managers email address : XXXX and I sent over all the paperwork to her. No response from anyone, and I received another bill of XXXX. I called on XXXX/XXXX/XXXX and talked to XXXX who transferred me to the research department and I spoke with XXXX. He promised me that he will personally follow up and will personally send my documentation to the research department and will notify me by phone. Again, no answer. I received an email from the research department stating that there is no mistake on their behalf and I owe them money. The research was done partially. I requested a full up to date research and they did not comply. I called back on XXXX/XXXX/XXXX and spoke with XXXX. I requested a supervisor named XXXX. She said the same thing that she was going to start a research again. And for me to follow up because she was going on vacation next week. Because she was no help I emailed back to the research department and requested a full investigation from day 1 until current. As of the day of this writing XXXX/XXXX/XXXX the issue is not resolved, and I am getting billed XXXX however my monthly mortgage is XXXX