co signer on a student loan with Sallie Mae

I am the co signer on a student loan with Sallie Mae. The loan holder is my ex husband. I have requested to be released as a co-signer. The company states this could be done after 24 months of consecutive payments. The payments were made and the release was sent to the loan holder, who said he never received it. That is completely unfair and unethical. I was also told at one time by one of the Sallie Mae representatives that with a copy of the divorce settlement and the divorce decree ( stating he would be the sole payer on the loan ) I could be released. The loan holder constantly changes the password to the online account. I get very little communication from the company. Every few months I get a letter stating the loan is past due. I have no clue if he even pays it on a regular basis until the loan is so overdue. I asked the company for payments that I have made. They never responded. I have made approximately $1200 in payments on this loan.