I put my old phones sim into iphone 3?

I had a motarola phone, and was on a contract and had all the things like 3g, texts, minuets. Then i was given an iphone 3 and i put my sim into it and texting, phoning all those functions don't work and it still thinks i'm the user who had the phone before - how can i fix this?

Go to the store and pay for the I phone service.

Try resetting the handset.
If the phone is SIM free then the SIM should work.