Is it permissible to demand a full refund of the amount paid for a Hajj campaign in exchange for dropping a complaint, given the poor services and the pilgrim's desire to perform Hajj again?

The institution must compensate you for the damage incurred due to the loss of a portion of the agreed-upon beneficial attributes. However, it is not permissible to take more than what was lost of that benefit, based on the Almighty's saying: "And do not consume your properties among yourselves through falsehood." Reconciliation does not make lawful what is forbidden. So, whoever knows that he is demanding something wrongfully is not permitted to take anything. It is sufficient to file a complaint with the competent authorities to hold them accountable. The advice is to accept appropriate compensation if it is offered to you.