What is the ruling on my working for an electronic payment company that adds a 2% or more gratuity for workers to the customer's bill, with the possibility for the customer to cancel this gratuity, knowing that many customers do not notice that they are paying the extra amount?

It is permissible to give tips to workers if it is with the consent of the giver and the entity employing the workers. It is not permissible to give it in a hidden way that the customer does not notice, because that is consuming wealth unjustly, and a gift is not valid unless it is with the consent of the donor. So, if the customer does not notice the discount, it is forbidden for the worker to take the tip, and it is forbidden for the issuing entity of the card to conceal this discount, because that involves aiding in consuming wealth unjustly. If the company insists on obscuring the matter, it is forbidden to continue working with them.