When you receive an incoming blocked call (which might display as "Unknown," "Anonymous," or "Private" in your phone caller ID), it can be irritating because you don't know if it's a call from someone you know or a call from a sales person or telemarketer. Fortunately, you can purchase services and products to unmask or stop these calls. You can also register your phone numbers for free with the National Do Not Call Registry.
Order blocking for unknown calls. Most landline, DSL and VoIP carriers offer a variety of blocking services for a monthly fee. For example, you can order anonymous call rejection (when a caller with a blocked number calls, a recording requests the call to be unblocked for it to ring through), call screen (while the unknown caller is on hold, you can reject, accept or send the call to voicemail), selective call forwarding (only phone numbers you list are forwarded to another phone number). Contact your carrier and ask which blocking services it provides.
Purchase a masking service. For example, TrapCall lets you customise how you wish to block incoming calls for any cell phone. You can unmask names and phone numbers of unknown caller IDs, set up a list of phone numbers to block, transcribe and send voice messages to a specified e-mail address).
Purchase an external device. There are external devices, such as PrivacyCall by Digitone Communications or TeleZapper by Privacy Technologies, Inc., that give you the ability to stop unknown calls on landline phones. PrivacyCall lets you block calls from pay phones, 800 numbers, those with blocked caller IDs, a list of numbers you wish to not ring through and more. TeleZapper works with your phone or answering machine to reduce calls from telemarketers by disconnecting calls before they ring through.
Sign up with the National Do Not Call Registry. You can register, for free, any landline or cell phone number with the National Do Not Call Registry (Donotcall.gov), which prohibits most telemarketers from calling your number. To register your number, go to Donotcall.gov, press the "Register Now" button, and follow the instructions. If, after thirty-one days, you're still receiving telemarketing calls, you can file a complaint with the National Do Not Call Registry.