Hi: I have a Blackberry 8130 with $9.99 Blackberry + $9.99 unlimited data plan. I want to get an iphone to use. Should i get a $99 Refurb 3G iphone and cancel my ATT subscription or try and get a used 2G iphone (~$250-300 on craigslist)? I am in the US. And with the Blackberry plan, do i need to change my data plan or will i be able to just replace the sim card? thanks.