Hi Monica,
When the client has shared the WSDL with Namespace then they should send all the requests with the namespace is there any specific reason they are not doing so?
Anyways what you can try is create a duplicate document for input with similar structure (Remove Namespace prefix for this document) as that of the generated one(with Namespace) and include it into the connector/service in place of the default generated one.
I am not sure if this works but you can give it a try and update us.
Regards,
Syed Faraz Ahmed
#webMethods#Integration-Server-and-ESB