Is benefiting from a free medical service that was neither approved by medical insurance nor recorded in the medical file considered a sin?

The work done by the physician with her own hands for the patients is not problematic, as long as it does not affect the work for which she is salaried. However, if the service involves using the hospital's equipment or dispensing medicine without payment, then it is not permissible, because it constitutes disposing of another's property. She must pay for that service or seek forgiveness from the hospital owner.