Is money earned from selling a used device at a price higher than its original price after adding a commission, or from selling items that the company does not sell, or from buying goods from the company and selling them to agents at a price lower than the company's price, permissible or forbidden?

Selling a used device can be done in two ways: Either you are a broker, in which case you must inform the buyer of your commission, and you are not required to inform him of the other agent's commission. It is stipulated that the commission for the agent must be permissible (halal). Or, you are a seller, and for this, three conditions are stipulated: that the sale takes place outside of working hours, that the buyer deals with you in your capacity as the seller, and that you own the device before selling it.

If someone comes to you wanting a product that your company does not sell, it is permissible to sell it to him, subject to the three aforementioned conditions. However, if an agent does not wish to buy from your company due to the high price, it is not permissible for you to buy the product from your company and sell it to him at a lower price unless the company gives permission, because you are an agent for the company, and an agent is not allowed to sell to himself in a way that harms the interest of his principal.