"This collection already contains an address with scheme http. There can be at most one address per scheme in this collection." is a Windows Communication Foundation (WCF) error message indicating you are trying to add an already existing binding. By default the web service listens to all in IIS configured host headers. A host header is the website address, for example example.com and www.example.com. If this is not correctly added to the web.config file, the following error is thrown