REST API - Service method not found

I have successfully read data from my REST API call. However, when I try to use POST method to execute a service method I am getting the following Exception from my application log (server side):

06:34:25.559 INFO c.h.a.r.a.c.RestControllerExceptionHandler - RestAPIException: Service method not found, erp_WorkflowService.approveTask()

Here is my Service method:

    public void approveTask(String workflowTaskNumber){
        EntityManager em = persistence.getEntityManager();
        WorkflowTaskLine workflowTaskLine = em.createQuery("select e from erp_WorkflowTaskLine e " +
                        "where e.workflowTaskNumber = ?1 ", WorkflowTaskLine.class)
                .setParameter(1, workflowTaskNumber)

Here is How I exposed the service in REST

<service name="erp_WorkflowService">
    <method name="getWorkflowTaskLineList">
    <method name="approveTask">
        <param name="workflowTaskNumber" type="java.lang.String"/>

And REST call from client-side:

 Uri.parse(constant.server_rest_path +

Is there any mistake in the code or is there any specific user authorization for the user to REST services apart from access to the table as a REST user and the following?

Thanks for suggesting how this can be fixed.

Oh… i found my mistake

I used ‘post’ but it should be ‘get’ in my service call: