Is it permissible for the contracted party to reduce or cancel the contract after its signing and after the first party has fulfilled all its obligations, especially when it demands unagreed-upon matters and procrastinates in disbursing dues, particularly after the change of the official who signed the contract?

The fundamental principle in dealings is fulfilling contracts and conditions, as Allah Almighty says: "O you who have believed, fulfill [all] contracts," and the Prophet, peace and blessings be upon him, said: "Muslims are bound by their conditions." Thus, the contract is the law between the contracting parties as long as it does not contradict Islamic law, and both parties are obliged to adhere to it. If one party defaults, the other party may refer the matter to the competent authorities to claim their right. And if a right is lost in this world, it will not be lost in the Hereafter, for Allah Almighty wrongs no one, and rights will be rendered to their rightful owners on the Day of Judgment, and the aggressor will be held accountable and some of their good deeds will be taken, or they will bear some of the sins of the wronged.