From a landline telephone:
1.) Get a caller ID. A caller ID is the device that attaches to your phone to identify the phone number (and frequently the name) of who is calling you. Don't pick up phone calls from numbers you don't recognize.
2.) Is it from a telemarketer? The single most useful tool to prevent telemarketers from calling you is placing your number on the Do Not Call Registry. You can place your cell phone and/or landline number on the list in one of two ways:
a.) Visit https://www.donotcall.gov/default.aspx and be sure to acknowledge the confirmation email
b.) Call (888) 382-1222 and follow their directions
All persons with a U.S. phone account are allowed to have their phone numbers placed on the Do Not Call Registry. Please allow 31 days from registration confirmation before telemarketers to cease calling. Registry enrollment is valid for 5 years.
3.) Get an "inbound call blocker". This is a screening tool that allows you to select who you receive phone calls from by giving them a special code along with your phone number. There are also numerous similar products that screen and block inbound calls. Check out some products at http://www.commandcommunications.com/index.php and http://www.privacycorps.com/products/.
4.) Also, call screening custom services may be available from your local telephone company. Be sure to confirm the company's prices for any such services, as they may be expensive if they charge per call. It may be cheaper if, rather than renting on a monthly basis; you just purchase any hardware or device from the phone company (e.g. a one time fee of $85.00 rather than $9.95 per month).
5.) Set up a "call screen": Your phone can reject calls from specific numbers with a Call Screen. Once the number is screened, it will reroute the call to a message saying that this phone number is not accepting calls from your phone number. The most recent call on a telephone line may also be screened, should you wish to block the caller who had just called you. Again check for monthly or usage prices.From a cell phone:
1.) View the caller ID and if it's from a number that is harassing you, don't pick it up. Reminder: Save the voicemails if the calls are from a harasser or a stalker.
2.) If the call is from a telemarketer, inform them that the number is a cellular phone and inform them that telemarketers may not call cell phones unless requested or consented by the phone owner.
3.) A cell phone works quite differently than a landline. Unfortunately, there are currently no methods for blocking specific calls from the user end of the cell phone. However, should you by stalked or harassed, many cell phone companies have corporate security departments that will work with you to stop the disturbing calls.