When debugging an application using web services, it's useful to look to the SOAP XML that is transmitting the request and response messages. A tool such as HTTP Analyzer (or a tool that you may already have in your library) can be used to view request and response messages. For your reference, the messages are encapsulated between
<s:Envelop ... ...
If additional troubleshooting is required, forward the messages (with sensitive field value masked) to your Integration Specialist along with your Merchant ID and a description of the issue.