How can i change the sim card in my blackberry?

i got a blackberry 8900 and my SIM card is with T-Mobile. I have an o2 one that i used in my old phone (Samsung D600) and i was just wondering if it's possible to use that SIM card in my new blackberry. If it is then what do i have to do, because when i tried to use it, my blackberry didn't recognise it and said 'invalid SIM card' or something like that.



help please. thanks.How can i change the sim card in my blackberry?
It is likely that your Blackberry Curve is locked and it will only work on T-Mobile's network. For it to work with any other network (i.e. using O2 SIM card or any other SIM card), the phone will have to be unlocked. Contact your network service provider if they are willing to unlock the phone. Most mobile service providers are quite reluctant when it comes to performing this unlocking during the duration of your contract.