Free restriction code are not possible for your mobile Nokia C3-00. Contact your network provider to get the code. If they failed to provide, you can get it from online providers. You should pay for the code to get that. Get the code from the site www.superunlockcodes.com/nokia-c3-00/rs16wp9/
here you should also provide network provider to which your mobile is locked, country to which the locked network belongs to and IMEI number of your mobile. Unlock it by yourself using simple step by step unlocking instructions which is given in the site itself.