First, the best advice for dealing with a hungry troll: don't feed him.
Ignore this guy, and he will quickly get bored and move on.
If your device runs iOS 7, you can block FaceTime and messages from known addresses that disturb you.
However, if unknown individuals are bothering you with frequent iMessage text messages, you can adjust your Notification settings to ensure that you are not interrupted with alerts when messages from unknown contacts are received (the messages will still be waiting for you in the Messages app, but you will not receive pop-up or banner notifications about them).
To disable notifications for iMessages from unknown contacts, go to the Settings app, then Notifications, then Messages, then scroll down to the "Show iMessage Alerts From" and select My Contacts Only.
Then, ensure that the person who is harassing you via iMessages is NOT in your Contacts. You should no longer receive alerts about his messages (but they will still be received in the Messages app).
Note that this also means that you will not receive notifications about messages received from ANY unknown contacts - you will only receive notifications about messages received from phone numbers or email addresses that are stored in your Contacts. So, be sure to check your Messages app regularly to see if you've received any messages from people not in your Contacts list that you WANT to hear from.
Do you want to place calls between two iDevices using the same Apple ID?
By default, all devices connected to the same Apple ID utilize the primary email address associated with that Apple ID. This means they'll all ring if a FaceTime call is placed to that email address. It also means you can't place a class between two devices, just as you can't use one home phone to place a call to your house and answer it with another phone. But luckily, Apple has provided a rather easy workaround for placing FaceTime calls on the same Apple ID.
To place a FaceTime call between two of your Apple devices, you will simply need to add a new email address to one of the devices. This will allow FaceTime to differentiate between the two and place a call to a specific device.
You can add a new email address to FaceTime in the iPad settings. Simply select FaceTime from the left-side menu and tap your finger where it reads "Add Another Email..."
Once you add a new email address, you must verify it by going to that email's inbox. There should be an email waiting for you from Apple with a link that will verify the email address.
Source - http://ipad.about.com/od/iPad_Guide/ss/How-To-Use-FaceTime-On-The-iPad_2.htm
Best Answer
Block that caller! And if he or she calls again just contact Apple and they will help you resolve the problem! Just follow my steps and you will be fine!