Still receiving data messages while on phone using EDGE

Today was my 1st time using wifi on my phone. And I discovered when I'm on wifi I can still send and receive BBM messages, as well as surf the internet. And I made a couple calls along the way.

Well when I switched my 'Mobile Network' settings back to what I think was originally 'Mobile Network Preferred' I continued to receive BBM, and Emails.

I thought this was pretty cool. Just letting ya know. I'm on T-Mobile btw.

Before I would have to wait to get on the phone before I received any data type messages.

I've come to think that I just answered my own darn question with just playing with my phone. In "Mobile Preferred' wifi was still running. Oh boy I feel dumb