Is it permissible to raise the price of a service that requires mediation and to collect the increase without informing the beneficiary, for the purpose of compensating for the effort and time expended in the mediation, and is this considered a permissible type of trade?

It is permissible to take a commission for the effort expended in coordination and communication, provided that the paying party is informed of the commission. It is not permissible to inform them of an unreal service price, because that is a lie, deception, fraud, and unlawful consumption of people's wealth. Moreover, it makes the person appear as a benefactor for something they did not do.