I'm not sure if this is what you're asking - but when I want to speak to several friends at once I call everybody. I call the first person and then after that when I place the cursor over a contact Skype asks if I want to add that contact to the call, and so on, until everyone is online. So they're not separate connections, and I think if someone tries to call me they'll get a busy message rather than getting to join in on the call.