Do I need to have a sim card in my iphone to unlock it?

I will need to cut my sim card to make it fit into the iphone because the sim card I have on my current phone is bigger than the ones for the iphone.

I want to use T-mobile as my carrier.
How exactly do I unlock my iPhone?

Check for factory unlock otherwise turbo unlock is avilable

First you check your iphone is Factory unlocked or not at: www.s-url.ro
if its unlocked, try to connect itune with your T-mobile sim

Now itune must 10.7 and ios 6 need to ACTIVATE

if your iphone is Locked status donot update your phone to ios 6

Iphone 4 and 4s can only be unlocked by the original carrier if your a customer off a 2 year contract.

You need to Unlock I-phone from current network provider to use other GSM Network sim card… To unlock it's specify the network, country it locked now, then get Remote Unlock service at http://www.wickedunlock.com/apple-iphone/rs11wp9/ and unlock it easily.