Is deducting days from one's salary or vacation balance in exchange for personal use of company property (such as phone, internet, and printer) justified to avoid the unlawful?

Previous fatwas have deemed it forbidden to use a phone or other work tools without the permission of the company or government entity. Your intention to compensate for the cost does not justify such use; rather, it is considered an aggression and an injustice, and the compensation may not be sufficient. The correct method is to seek permission from the authorized official.