vb.net VOIP capability (1060721)

We need a VOIP capability as part of our contact tracking database system. Visual Studio 2008 with VB.NET is our development environment. We prefer an off-the-shelf existing commercially available software package that we can incorporate in our application with little or no difficulty. However, all alternatives will be considered. Basic Functionality In our vb.net application, the user can enter a telephone number, e.g. 617-555-1212 in a text box. When the user clicks CALL, the VOIP package will establish the call. The user can click a button to end the call at any time. Only this basic functionality is needed at this time. We will add additional functions (e.g. call-logging, recording of calls, etc) in a later edition. Please respond with a suggested commercial package, and time and price to develop. We are looking for someone who can carry out VOIP development tasks through calendar year 2009.