Is it permissible to take from the company, without its knowledge, a health insurance [benefit] that I was deprived of due to a slanderous report?

It is permissible for an employee to stipulate cooperative health insurance from the institution, and the institution is obliged to fulfill it. Non-cooperative insurance is not permissible, and if the institution provides it, the employee is not allowed to take more than what was paid, due to the invalidity of the contract. If insurance was not stipulated and the institution refused, the employee is not allowed to take anything from its money. However, if insurance was stipulated and the institution did not fulfill it, then the employee may take what is due to him, and this is called the issue of "al-Dhafr" (seizing one's right).