service endpoints behind load balancer

Dear All

I am pretty new to soapui, so maybe my problem is trivial and some of You already know the answer.
We have a system consists of 2 layers, each of them is sitting behind a load balancer (LB).
The first layer is a 2 node IIS cluster, the second layer is a webservices gateway 2 node cluster (Linux).
I am creating a sample test projects in UI:
- for the first layer (IIS) I specify the first LB address and the wsdl gets downloaded but the service endpoint remains the same (it contains the url of the load balancer)
- for the second layer (WS gateway in Linux) I do exactly the same, I specify the second LB address, the wsdl gets downloaded but the service endpoint is changed (it contains the url of one of the nodes which are behind load balancer).

It is an issue for our interconnected systems/customers - because they will have to adjust the address each time they create a new test case (there will many of them).

Does anyone of you can help me to find the root case?

Many Thanks in advance
Best Regards
lukasz