A co-worker and I are in disagreement about Blackberry's. I say you can not BBM someone who has a BB but no data plan. He states that you can, through RIM? The person he is in question about has ATT service.
some carriers offer an email/IM plan, which isn't a data plan per se but gives you BIS functionality so you can use email and BBM. But yeah you need some kind of BIS access to use BBM.
You need data CAPABILITY; not necessarily a data plan. Some providers will set it up in a pay-per-use way if you don't have a data plan. I am not aware of any carriers that do this any more for blackberries. In the US it's pretty difficult if not impossible to get a blackberry without a data plan. If you don't have a data plan your data service doesn't work.