Can I Use My Iphone Sim In Blackberry for bbm ???

hi, i am on a really good iphone simplicity 12 month contract with o2, but have purchased a blackberry curve 8520 as a spare/college phone, and will be using it for 2 months while selling my iphone ready for i5, but anyway, can i add the blackberry bolt on to my iphone contract to use in the blackberry? i dont want to change tariff, as when i get my i5 (payg) i might not get the same deal back from o2, as my current tarrif has already stoped (300mins,unltd txt, 500mb internet, unltd o2-o2 calls all for �15 per month) thats to good a deal to risk, so i want to add blackberry services and dont mind paying the extra �5-�7 for it, is this possible? thanks