According to Verizon Wireless, "Neither Verizon Wireless nor any other wireless provider is able to block specific numbers from your wireless phone; however, we are able to block all incoming calls. We strongly recommend that you utilize your Caller ID feature to screen your incoming calls. This way, you will be able to ignore unknown callers at your discretion. If the unwanted calls persist, we encourage you to change your wireless number." Hope this helps you.
I forgot about Verizon's Usage controls. In My Verizon, you can log into your account and block specific numbers. Look here for detals on how to do it.
Sorry for the confusion
*Thanks to LCromwell for setting me straight..