Webservice Design (Parameter)

Hello,
I'm developing an application (C #), which communicates with Navision via webservice.
This program runs on about 15 Clients.
Now I use currently about 20 pages and 30 function of a code unit via webservice. (I develop on a testsystem).


And here I have now my design problem. If I have to change a function in a codeunit , add or remove a parameter.
When I transfer this CU to the productive System, the C# application got an error when calling this changed function.
Must always all clients to update immediately.

How could I solve this.

Thanks
stony