BIS with regular data plan?

I'm new to the Blackberry and I want to set up BIS to get my email. But here's the question: Do I have to have a Blackberry plan or can I use my existing regular data plan? To be clear, I am coming from a WinMo phone so I have a $20 data plan that gives me unlimited data and enough texts for my usage. The data features on my BB work just fine with this plan. But I am wondering if setting up my BIS will make the system "notice" that hey I'm using a BB without a BB-branded data plan. I'd like to avoid going to a more expensive data plan if possible.

Thanks!

Gotta have a BB email or data plan if you want BIS. Any other plan isn't BIS.

i was the same way and only using media net. after i changed to BIS data plan its worth every penny.