@RestResource(urlMapping='/QueryRecords/*')
global with sharing class QueryRecords{
     @HttpPost
     global static void updateRecords(){
          String mobile = RestContext.request.getParameters().get('Mobile');

          List<Contact> contactList = new List<Contact>();
          List<Lead> leadList = new List<Lead>();
          List<Task> taskList = new List<Task>();

          contactList = [SELECT Id, Name FROM Contact WHERE MobilePhone =: mobile];
          leadList = [SELECT Id, Name FROM Lead WHERE MobilePhone =: mobile];

          for(Contact obj : contactList){
               Task objTask = new Task();
               objTask.whoId = obj.Id;
               objTask.Description = mobile;
               taskList.add(objTask);
          }
          if(taskList.size() > 0){
               insert taskList;
          }
     }
}