Is it permissible for employees of a company that sells mobile cards and lines to take cards or lines from the company and sell them for their own personal gain, paying their price from their own money?

It is permissible for employees to earn through this action if it is authorized by the company's management, or if it is customary for employees to do so without objection. However, if the action is unauthorized, or if it is customary to prevent employees from doing similar things, then it is not permissible to practice it or earn through it.