WCF SERVICE - wsdl Schema location problem behind firewall

Hi everybody, it’s almost 2 days that I’m going crazy with the following problem:

We’ve developed and correctly tested in our development system a new WCF service.

Our production server, in DMZ, is positioned behind a firewall redirecting the external IP (IPEXT) to an internal one (IPINT)

http://IPEXT/App/Servizio.svc?wsdl

unfortunately the schema locations on the wdsl are wrong because they are directed to the internal server:

.....
<wsdl:import namespace="http://IPExt/App/" location="http://IpINT/App/Servizio.svc?wsdl=wsdl0" />
- <wsdl:types>
- <xsd:schema targetNamespace="http://tempuri.org/Imports">
<xsd:import schemaLocation="http://IpINT/App/Servizio.svc?xsd=xsd0" namespace="http://tempuri.org/" />
</xsd:schema>
.....

In fact if I include the service in a client on the local network it works correctly, but if I do that from a client in the intranet…it doesn’t work (obviously he doesn’t know who’s that local network name)

Please is someone able to tell me a way to force the schema location in my web.config file of the service?

Hope that my explanation of the problem is clear!

Thanks a lot for all the help!