Could not load file or assembly error even when the old DLL was renamed

Question

In my VS 2013 solution, I have few projects like:

1. BookService.BusinessLogic
2. BookServiceContracts
3. BookJob

The BookJob project is a console application which references the services: BookService.BusinessLogic and BookServiceContracts. The INetPub folder contains DLLs of BookService.BusinessLogic and these are invoked when job is executed.

The application was working fine. Recently there was a requirement to add a code in BookService.BusinessLogic project. I added the code, recompiled and replaced the BookService.BusinessLogic.DLL and BookService.BusinessLogic.pdb in INetPub. This is when the problem started. The EventViewer is logging errors something like this:

Exception=The content type text/html; charset=utf-8 of the response message does not match the content type of the binding (text/xml; charset=utf-8). If using a custom encoder, be sure that the IsContentTypeSupported method is implemented properly. The first 1024 bytes of the response were: '

Could not load file or assembly 'BookService.BusinessLogic_old' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference.

I renamed the previous DLL in InetPub folder as BookService.BusinessLogic_old, but the job is still pointing to the old DLL it seems. How to fix this reference issue?