First of all, are you sure that they are really misusing your documents ? secondly, why have you handed over your originals to them ? Legally employer can only take your documents for verification purpose only and it needs to be returned back to the employee on completion of the same. Also, No employee is authorised to withheld any original documents with them. In your situation do you have any written proof of submission of your original documents to them ?
You may try to use legal help in this manner and before approaching the same you may convey the same to them verbally which may result in returning of your original documents. 3rd July 2018