What is the ruling on the action of a maintenance worker who increases the price of spare parts for a customer to achieve personal profit, while giving the customer the option to purchase the part himself?

The maintenance worker acts as an agent for the owner of the machine in purchasing the required part. It is not permissible for him to take more than the price he paid for it, unless with the knowledge and approval of the machine's owner. Otherwise, he would be consuming wealth unlawfully, based on the Almighty's saying: "And do not consume your properties among yourselves through falsehood" and "O you who have believed, do not consume your properties among yourselves through falsehood."