AFAIK there is no generic unlock code. It depends on the IMEI number of the phone. You will find unlock services on the Internet. Ebay sellers usually offers competitive pricing too.
I agree . But unlocking has a few variations.
Like unlocking the sim lock with the network (Typically in this case you will get Invalid Sim card display and SOS calls only when you insert other network sim ),
Unlocking / removing the IT policy,
removing the password . etc.
As suggested by PaulMDX, you can pay and get am unlock code or if you want to unlock yourself , you can try looking at the various posts in this forum specifically for this. I had used a lot of them and found to be incredibly easy.
Pls ask with specific details and i will send you the links