It can be very frustrating to receive calls from people with whom you do not want to speak. Fortunately, there are some ways to prevent a specific number from calling you on your landline phone. Various telephone carriers let you do this with a call restriction feature; if not, you can try getting the number blocked internally from your phone set.
Find out whether your telephone company offers services like call blocking and unidentified call rejection. Each company has different features but they work more or less the same way. Upon calling the concerned representative at the telephone company, you will be issued a code that is to be dialled on your landline phone to block the last number on your incoming calls list. You can just dial the code right after you receive a call from the number you want to block. Alternatively, if you avail the unidentified call rejection feature, every call from an anonymous or "unknown" number will automatically be terminated by your phone.
Register your landline number on the National Do Not Call Registry online. It is a free service that allows you to put your number in the list that telemarketers are prohibited from calling. For registering your number, visit the website Donotcall.gov.
Go through your telephone set manual to find out if you can block a number from the phone. Many cordless phone sets support this feature. For instance, if you have a Panasonic phone, you can simply create a "Block List" and feed the Caller ID information of numbers you want to block. The numbers you store in this list will get a busy signal upon dialling your number.
If you receive harassing or threatening calls, note the time and number of the received call, and notify your cell phone company to take the necessary measures against it.