Lock down calling for Iphone

A friend of mine wants to lock down her son's Iphone so that he can only make / receive calls from people in his contact list. Anyone know of any apps that can do this? Additionally can you recommend any apps for locking down other functions of the Iphone?


Thanks in advance.

parental controls in settings.

Thanks for that! I found theses instructions based on your suggestion and this will be good for the non calling lock down 

 http://support.apple.com/kb/HT4213

doesn't look like it can restrict calling though or am i just missing that?