Web-based VOIP application

I'm going to make an small call center application with ASP.NET. In this application the user will call the customer. However I've already learnt开发者_StackOverflow中文版 that there is no way to make an ASP.NET-based VOIP application.

Now, If it can be done with Silverlight, I want from you some reference, links or samples.

If it's not possible, I want some other advice. Maybe we can pass parameters from an ASP.NET application to another application (Java applet, Flash or Windows app).

What about internet phone services that use a different technology like for instance php or others. Like axvoice or vonage might be using a different programming language at the back end. Will it be compatible with services using other web development languages.