The 'Access-Control-Allow-Origin' header contains multiple values Wordpress Website and Parallel Plesk(windows Hosting)

Question

I am trying to access web service in my phonegap project but this is showing me this error The 'Access-Control-Allow-Origin' header contains multiple values '*, *', but only one is allowed. Origin 'null' is therefore not allowed access.

The Website is in wordpress and hosted in Parallel Plesk(windows Hosting).

I have also added this in web.config but i did not succeed-

<httpProtocol>
        <customHeaders>
            <add name="Access-Control-Allow-Origin" value="*" />
                <add name="Access-Control-Allow-Headers" value="Origin, Content-Type, Authorization, Accept, X-Request-With" />
                <add name="Access-Control-Allow-Methods" value="GET, POST, PUT,  DELETE, OPTIONS" />
                <add name="Access-Control-Allow-Credentials" value="true" />
        </customHeaders>
    </httpProtocol>

Any Help would be appreciated, Thanks in advance.