Message signing in wcf using x509 certificate

I am facing an issue while trying to consume a WCF web service which requires mutual authentication and message signing using X509 certificate. I have already implemented mutual authentication using X509 certificate, but I am facing an issue while trying to implement message signing. I have successfully installed certificates on my machine. The error message I am getting is:

Signature verification failed

Please note I have successfully tested this application using SoapUI. But I am facing this issue while trying to implement the same in C#.