I just spotted another issue with your code. Your service isn't picking the binding!
<endpoint address="" binding="netTcpBinding" name="netTcpBindingEndpoint"
contract="CredoService.ICredo" />
needs to be
<endpoint address="" binding="netTcpBinding" bindingConfiguration="netTcpBinding" name="netTcpBindingEndpoint" contract="CredoService.ICredo" />
in your <services><service><endpoint>
section.
That would explain why VS is going with default NetTcpBinding instead of your options.