Hi Ahmed,
Please share the code you tried. Also I recommend that you could download the package shared and follow the steps in Invoke webMethods IS policy in API Gateway 10.1 and below (link already shared in prev comment from me) to get a hands-on with how to do programming using MessageContext (if not already done).
If you are using MessageContext coding in later versions (10.3 or above), you could configure “Comply to IS Spec” policy configuration as “False”. More details can be found here Invoke webMethods IS policy in API Gateway 10.2
Regards,
Vallab.