I'm not aware of any, but IOS 7 is supposed to implement this feature. With any luck it will be available next month.
As of February 2008 the registration does not expire so there is no need to renew.It depends on what kind of calls they are? If they're advertisements, make sure your number is on the US "no call" list. And if they have the same service in your state (Texas does have it) sign up for the state wide no call list also. I have my wife's and my numbers on both no call lists. Your number will remain on the US no call list for 3 years and can be renewed.