iphone & blackberry help?

I have an iPhone 3g. I was wondering like if I wanted to get the new BB Bold, i could get that at full retail price, and then change my data plan to an BB data plan on the internet w/ our wireless account? after i put the simcard into the Blackberrry Bold 9700? please let me know if that would work.. i mean i know they both have diff data plans like blackebrry data plan and iphone data plan, but cant you edit it online w/ ur wireless account and just switch the sim card? If so, i want to do that. i do’nt have like an upgrade which is why i would get it at full retail price. so yeah. help me and thanks in advanced And YES I know there are two different data plans that cost the same. don’t tell me that they are the same plan..The blackberry’s is called: Blackberry personal (or the one i’d get is personal bundle? or if i’m just switching just the personal bundle b/c my family already has unlimited messaging..) and the iphone’s you just choose it when you’re on the phone. like if you go to buy it. and it says data plan for the iphone..)