What didn't work? If you are refering to the fact that it doesn't block calls, No iphone app from the App Store can do that. Apps downloaded from the App Store are prohibited from touching that level of the OS. If you have a jailbroken iPhone and have downloaded a version from else where, we can't help you here.
Don't know exactly which iBlacklist app your trying to use, but you should have read the description and ratings for the app. The ratings for the apps I've seen aren't good at all.