I have a class like
public class CreditCardDocumentImpl extends org.apache.xmlbeans.impl.values.XmlComplexContentImpl implements creditcard.CreditCardDocument {
Did you generate these classes through CXF using XmlBeans? If so, probably your interface provides a public static property with the schema type, or even better, you can try:
CreditCardDocument creditCardDocument = CreditCardDocument.Factory.newInstance();