Product: Student loan

I used to always pay my student loan payments on time. However, last XXXX of this year ( XXXX ) I lost my employment and have been unemployed for most of the year living with just part times and unemployment benefits. I explained many times the situation to Sallie Mae when I noticed my student monthly payments continued to spike higher and higher and I could no longer pay them. I asked for some sort of temporary debt relief program with lower payment. 95 % of the time they told me I did not qualify for anything in my case, and that the only program that they could offer me after interviewing my co-signer financially would be a specified amount they determined, not what I could actually pay, once we went through that process, I quickly learned $ XXXX month would still be too high in my circumstances. I continued doing the best I could, making payments of at least {$120.00} a month, which was what I could afford at the time. I kept getting behind on my payments however, and eventually the debt harassing started. Calls day and day out nonstop, to my personal cell, my house, emails, texts, and letters in the mail to both myself and my co-signer. Eventually I found a job in XXXX. One day out of many I called them to try to work something out with them to where I could actually repay and get caught up, one of their reps ( " XXXX '' XXXX ) offered me a graduated repayment program. She said she would sign me up for twelve months, making graduated low payments of {$93.00} a month. She interviewed me, collected my name, social security, and bank information and we proceeded with the agreement interview over the phone. Finally she gave me a confirmation number : XXXX XXXX on XX/XX/XXXX. She said it would just take a few days for that to reflect in my account. Later the same day she called while I was working and left voicemail requesting I call her back regarding our previous conversation. Never did because I was busy and found it odd. 
However, not seeing any change to my account online on the Sallie Mae Portal I called the XXXX number and spoke to a rep then a manager and they told me I needed to repay the past due amount of almost $ XXXX immediately or they would report me to credit reporting agencies. I was confused. Then, they told me that the said agreement I had signed up for to repay did not exist in their records and that it never happened. 
They have continued to call, harass, and try to collect debt despite that agreement. From conversations with them it sounded like something happened on their end where they made a mistake and just revoked the agreement without notifying me or my approval. I asked said I understood if they made a mistake, but just wanted a similar program if not that one to finally be able to repay them and get back on track. They refused, said there was nothing they could offer me. 
Recently they reported me to credit reporting agencies and negatively affected my score and my co-signer who happens to be my mom who is retired from a XXXX XXXX and sometimes lives in XXXX with her family. I want someone to do something about this. My only mistake was borrowing from advantageous companies like this to be able to pay an education.