Need to unlock it so i can use an o2 sim. currently locked to t-mobile

I think your mobile is locked by particular provider. So only it doesn't accept your 02 sim card in your mobile . If you want use o2 sim card in your mobile first you must unlock your mobile. You can easily unlock your mobile by using unlock code. If you need unlock code you can visit this site Wickedunlockcom here you can get the code and unlock your mobile easily. To get the code you have to mentioned your mobile brand name,model,which country is locked now,network provider and imei number. Then they send unlock code through email.
Wickedunlock.com

You need to unlock the network lock of the Samsung sgh-e250 to use it with other network Sim card. You can use unlock code to unlock the network lock. You can get the unlock code from Mobile-Unlocker.com . There you have to give your Country and current network name along with your IMEI number to get the unlock code. They will give you the unlock code along with instruction on how to unlock. Follow the instruction correctly and unlock your Samsung sgh-e250 .

NP code and Network unlock code are same...You can get the unlock code from the site
Onlinegsmunlock.com/t-mobile-e200-vibe/rs7wp9/ and unlock Your T-Mobile E200 Vibe Phone from network lock (T-MOBILE LOCK) Then use O2 SIM CARD IN IT.

You need to Unlock I-Phone 3GS from current network lock to use with other GSM Network Sim card...Get the Remote UNLOCK SERVICE from Theunlockspot.com/apple/rs10wp8/ and unlock it easily.

"SIM Lock" means that your are locked to o2 network and you cannot use other provider's SIM in your mobile..in order to get rid of this problem you have to unlock your mobile..you can unlock your mobile by unlock codes and its the safe and best way of unlocking..and also don't try with hardware/software unlocking because there is risk involved..for unlock code you can contact your provider or can get it from online providers..one of my friend got unlock code for his mobile from simpleunlocking and unlocked his mobile..you can too try getting codes from them to unlock your mobile..

hi if your phone is locked with o2 then you must first unlock it to accept orange sim .you can use codes to unlock your mobile , you can get the codes from here superunlockcodes here they ask the following details before rendering the codes they are
1.mobile model
2.country from where you brought the mobile
3.provider to which the mobile is locked
4.imei number of the mobile
finally they will send you the unlock codes once
you entered the codes in your mobile as for the instructions provided by them
then your mobile get unlocked and it will accept other network sim.

To get the security code/restriction code to unlock thecell phone from the current cell phone provider so you can use it with adifferent phone provider, Please click on this link and follow my instructions:- http://www.fixya.com/support/r4049238-unlock_cell_phone If your phone provider does not help you then this WEB siteit provides security codes for a small price. http://www.mobileunlockstore.com/?gclid=CKDb2_y2558CFSlJagodxBkDHw Try this WEB site also - UnlockFree http://www.unlock-free.com

RebelSIM II is the easiest option.
You simply place it on top of your current o2 sim and it's done!
Takes all of 10 seconds - and the bonus is that it does NOT invalidate the warranty of the phone.
More info at http://www.rebelsimcard.com
Hope that helps! It's certainly much easier than searching around for unlocking codes (which in many instances are a waste of money as they don't work).

To Unlock the Mobile from the Network Lock You can use the Unlock code,You can get the Unlock code at
http://www.wickedunlock.com/supported-phones/rs11wp7/
and Unlock the Mobile from the Network Lock.

You can try a mobile store close to you that unlock phones, or you can try online mobile2mobile.net or unlockitnow.com.