several student loans with Navient

i hade several student loans with sallie mae, and could not pay them all i had them consolidated into one. Sallie Mae then sent me a bill advising me that i still owed them 141.56. i called the consolidation company any they advised that they paid the bill that was sent wich was over 49,000.00 in total they advised that then Sallie Mae sent a nother bill after the process was done and they refused to pay this bill that just appeared. If Sallie Mae refused to send the total bill or what ever the issue was. being on disbility i cannot pay more than one bill.