There's also a program called "BerryBlocker", but I couldn't get it to work correctly on my pearl. It looked like it basically just provided an interface to set up exceptions (sort of) to your profile; being as how it didn't really block
the calls; it just didn't alert the user. The call was then able to go to voicemail.
The easiest way to do this is to set up exceptions to your profile to where you are not alerted when a certain person calls. If the person is leaving you voicemails, you can try a service such as youmail.com (I use this and it works great) which will enable you to not accept voicemails from any numbers you choose. And you can even set up voicemail greetings specifically for each number. I use a recording that says "please check the number and dial again" or the like for people whom I don't want calling me and then I don't give them the option to leave messages. Works wonders with bill collectors