What is the ruling on using a health insurance card that does not belong to me for treatment?

If the health insurance is a legitimate cooperative one and stipulates that treatment is only for the cardholder, then it is not permissible to violate the terms, based on the Prophet's (peace be upon him) saying: "Muslims are bound by their conditions in what is permissible." However, if the insurance is impermissible, its holder may benefit from it to the extent of what he contributed, because this falls under the category of seizing one's right. Therefore, there is no harm for you in receiving treatment with his health card if he permits you, provided that the benefit does not exceed the amount paid by the cardholder. And upon him is to terminate the contract if the insurance is not compulsory. It is not permissible for the insurance holder or anyone else to benefit beyond what was paid.