What should we do with a sponsor who wrongs us and forces us to sign papers proving receipt of our rights while we have not received them, and also blank promissory notes? And can we take our rights without his knowledge?

The contract is the law between the contracting parties, as long as it does not violate Islamic law. Violating its terms by causing a loss of rights or harm is forbidden injustice. The examples mentioned cannot be judged definitively; the contract is the decisive factor. If the employer denies the worker's right, the worker may sue him. If it is difficult to obtain the right through overt means, it is permissible to take it without the knowledge of the right-holder, provided there is no transgression. The employer is not allowed to force the worker to waive his established rights.