why cant I say Wei Bitte? I thought that is also a way to say your welcome
You're mixing up several things here.
- Wie bitte? is something you say when you didn't hear someone properly. "Excuse me? What was that? Come again?"
- bitte has several meanings -- one of them being a response to thanks: "you're welcome! don't mention it! no worries!"
- "Hello, welcome!" is saying that you're glad someone has arrived. It has nothing to do with thanking nor with not hearing something correctly.
I think it's pronounced Vil-koh-men - a minor difference, I know, but maybe that's throwing the program off.
Here's a great site, by the way, to learn how to pronounce basic German phrases: http://www.ielanguages.com/German1.html. It even has audio, like forvo, so you can hear the word flow.