When working with Web API, it is important to return data in the response in form of JSON Data so that a Client consuming the data won't do much to clean the data. You could append or define a format of data expected to be returned in the Http Header when making a request, however, in this case, we want to return pure JSON and make it a Web API standard.
Solution:
Just add the code below in the WebApiConfig.cs file and problem solved:
+1 888-688-2939 
