Product: Student loan

I have made on time monthly payments on my XXXX loans with Sallie Mae since XX/XX/XXXX. Both me and my co-signer were sent notifications that my repayment start date was XXXX of XXXX. 
XXXX of XXXX, my account showed no-payment required. The following months XXXX and XXXX also showed no payment required. During those months I did not make a payment because I was unsure of what that meant. Sallie Mae then resumed payments in XX/XX/XXXX with no notice. A late payment was automatically applied during XXXX and that is when I began calling. I was told incorrect payment amounts from different agents. My co-signer called and was told different information. When I made a payment in the amount of {$2300.00} for XXXX and XXXX in XXXX to bring my account up to date and figure out what the XXXX month hold was. I also gave verbal authorization for Sallie Mae to take an additional {$500.00} the same day. This was mis allocated and XXXX loans did not receive payment while other were over paid. I opened a case to have this resolve and only XXXX were fixed. They kept calling saying I was short on payment when I kept telling them I paid more than the required amount and I shouldnt owe anything. They constantly call asking for payment and applying late fees. When I called my corporate account XXXX XXXX, she began with telling me the money was not there and was demanding payment but after an hour found the money already in my account and said she would open a case again to have that fixed. I asked how will this mishandling of my money affect my co-signer release application and what were the XXXX months of no payment. she told me those XXXX months were placed in deferment by corporate. 
When I asked how will that affect my co-signer release. She could not and the question and directed me to someone who was suppose to be able to answer the question. I spoke with XXXX from the escalations department and she could not answer the question either. 
I was transferred back to XXXX and after XXXX hours I discovered my loans repayment start date was not until XXXX of XXXX. Yet the online portal and all of my statements show payments required from XXXX of XXXX. She told me all my payments do not count towards the release agreement because on her end I was still in a grace period. My end showed my grace period ended XX/XX/XXXX and payment began XXXX of XXXX. She admitted to a discrepancy in my account and couldnt answer my question as to how this will affect my co-signer release. Saying that I was already denied. When I said I was denied based on inaccurate information she gave no form of resolution. Just asking for payment. I told her I do not trust my account and money has been handled correctly from the beginning and will not make anymore payments. I will also be opening an investigation on my account to be sure no other discrepancies are found. 
I asked for all the documents she has as well as records of the conversation, she told me she will email them to me. She did not. 
When I called again I spoke with a difference account XXXX who told me XXXX did not open a case to fix the second Mis allocation of my money, she not take certain notes on the conversation, she gave false information about my accounts and about being able to email documents. This agent then went on to tell me she would open a case herself and request the documents are sent to me. I still have not received information pertaining to my account. 
They are still calling demanding money but will not resolve the discrepancies in my account. 

I also received an email from Sallie Mae saying a payment was received that cleared my account and paid off my loan. Please look into this as well. There is too much misinformation and mishandling of funds in my account for me to trust them and keep paying.