Say, after defining messafes according to your generated schemas – do you use WebPort type? (right click on port surface area – new port port name – port type – use existing port types – select from “WebPort Types” – your port)?
According to this error/post http://www.eggheadcafe.com/software/aspnet/30267049/setting-webservice-destination-programmatically-at-runtime—.aspx