Will O2 give me a micro sim?

I have a 2 year contract with a blackberry bold 9790 but my sister is giving me her old iPhone 4. I know you have to use a micro sim so if I cut my current sim card down will it work In an iPhone? I don't really want to risk cutting it so would O2 transfer all my stuff onto a micro sim so I can use it in an iPhone but still be on the same contract so I wouldn't have to cancel my contract now? I really want to use an iPhone and can't afford to cancel my current contact, any ideas?

I'm not sure about O2, but when i asked 3, they said they would just cut it for me, free. If your sister was on a different network, make sure her phone is unlocked - all you have to to is phone the network and ask them to unlock it.