Is it permissible to benefit from the service of reimbursement of treatment expenses from an insurance company without a deduction from the salary, whether in the case of comfortable financial circumstances or in the case of necessity due to high expenses?

The question is not entirely clear, but it seems that the questioner intends to unlawfully seize money from an insurance company. This is forbidden in both ease and hardship, as the wealth of people, whether righteous or wicked, is inviolable. If the questioner means that he can receive medical treatment at the expense of the insurance company because his company provides him with health insurance, then this is permissible within the limits of the amount paid by his company. Anything beyond that, he has no right to.