If you want the RIM services such as BBM, email, Facebook, maps, BB browser, etc., then you must have the BB data plan. Is that what you are calling The Blackberry ISP? What do I need a Data Plan for? - BlackBerryFAQ
If you are trying to set up WiFi, it depends upon your cell carrier. Some require the BB data plan to get the service books, others do not. Since you didn't list a carrier, I can't say. http://www.blackberryfaq.com/index.p..._BlackBerry%3F
And please update your profile to indicate your cell carrier. I know it isn't Time Warner. That info is helpful when you have a problem.