Yes, the phone carried company will charge you $50 plus tax to unlock your phone after 90 days of purchase. However, at least your manufacturer's warranty will still be valid. But if you want to unlock it for cheaper price and sooner than 90 days without voiding your manufacturer warranty, then you should consider paying for unlocking services such as http://www.cellunlocker.net and other online unlocking websites available.
You can also use the free unlocking instruction available on the internet but then these methods if not done correctly could potentially damage your phone software and void your manufacturer warranty.
If you go for the unlocking by the phone carrier company, you will be asked to provide your IMEI number which can be found in the settings information of your phone device. After that within 24 hours, your phone will be unlocked and you can use it in most places around the world.
If you decided to use the online unlocking websites, then you must also provide your IMEI number and email address. They will send you the unlock code to your email address you provided and all you have to do is to insert the new local sim card you intend to use (Not the original phone carrier sim card) and punch in the unlock code. A reboot of the phone might be required after inserting the new sim card depending on your phone model type. After that you will see that your phone is unlocked and all the signals are showing on your phone's screen. Do not insert the original phone carried sim card because then your phone will not ask for the unlock code on reboot. Its only when you insert the new sim card that you intend to use, the phone will then ask you for the unlock code.