Product: Debt collection

Citibank N.A. continues to report non-payment on my credit reports every month but has repeatedly told me via phone conversations they no longer own my loan and has sold it to XXXX XXXX XXXX who has also said they do not own loans but only service them for Citibank. XXXX XXXX has also informed me they do not have my account. Neither of these companies are able to tell me where the account is and who to pay and therefore it needs to be removed from all 3 reports immediately dating back to the day of inception. Details below : I obtained a private student loan with Citibank in early XXXX to cover tuition federal loans didn't cover for my XXXX degree with XXXX University. I noticed Citibank on my credit report in XXXX. I remained in school to obtain a XXXX XXXX and therefore placed all loans in forbearance. XX/XX/XXXX, I contacted Citibank to begin making payments. A representative informed me, my loan was sold to XXXX XXXX services the summer of XXXX. I had not received any information from Citibank or XXXX XXXX about the loan having new ownership. During this conversation, I asked to speak to someone in the student loan department to clear this up and receive proper documentation of my loan being sold ; but was told Citibank no longer had a student loan department. However, I noticed Citibank continued to report non-payment to all 3 credit bureaus every month. 
In XX/XX/XXXX, I disputed what were now 2 accounts Citibank had on my credit reports. 1 was a charged off account in the amount of {$2600.00}, the other was some kind of closed account. The charges did not fall off and Citibank continued to report non payment consistently each month. 
In XX/XX/XXXX, I once again disputed Citibank to no avail. While in dispute in XX/XX/XXXX, I called Citibank once again to obtain documentation of the location of my loan ; I was told they no longer service student loans and was transferred to XXXX XXXX. I explained the situation from the summer XXXX until current and was told by a XXXX XXXX rep that they do not own loans but only service them for Citibank. XXXX XXXX asked me for all of my personal information in an attempt to pull up my account. I went through maybe 3 XXXX XXXX reps that day and neither one of them could pull an account using any of my personal information. I called Citibank back again the same day and actually got the same guy I'd spoken to hours earlier only to get the same information, " ma'am we can not help you, there is no student loan department here ''. But somehow Citibank continues to report to the credit bureaus for non-payment of the student loan. XXXX XXXX has not reported anything on my credit report. 
Citibank reportedly sold the account the summer of XXXX and has reported non-payment of the loan every month since then with the latest being XX/XX/XXXX which is tanking my credit score I'm  working so hard to increase. I'm in the process of purchasing a home and this has been THE biggest thorn! 
I would like this removed from my report dating back to when they sold the loan. I would like Citibank removed completely as I was never given any notice of the loan being sold to XXXX XXXX. XXXX XXXX is not on my credit report. I would like all Citibank accounts removed from my credit reports. If charges can be pressed for false reporting, I'd like to look into that as well.