SIM card, and replace it with the new SIM card for a carrier other than the one which is your current carrier.
3. Power on your phone.
4. The phone will ask you for a GSM unlock code.
5. Simply enter the unlock code you were given and click OK.
That’s all there is to unlocking your HTC Desire S! Once you have successfully unlocked your phone, you will be able to use any GSM carrier for your HTC Desire S.