When we design the report the parameters are copied from the contract class and the details for them are stored in the report parameters.
In case that we later change the parameters in the contract class and the same are not refreshed in the SSRS Report parameters, there is a possibility that we will continue to see the parameters even though they are deleted from the contract class. This is due to the fact that the parameters are being fetched from the SSRS report.
To get rid of the issue, delete all the parameters in the report design, and restore the dataset again. When the dataset is refreshed the required parameters are automatically added to the report.