What is a one-sentence summary of the following article?
Most phone companies allow you to block a limited amount of numbers. These blocks may expire, however, so it’s important to keep the list updated if you receive abusive phone calls after the block has expired.  Many phone companies allow you to block up to five numbers for free. These blocks usually expire after three months. If you need to block more than five numbers, you may need to pay a monthly fee. This will also let you block the abusive numbers on a long-term basis. You can also try to get call rejection, which will prevent unknown numbers from reaching your phone. For some phone companies, you may be able to supply a list of ten or more numbers that will be rejected from calling you.  Anonymous call rejection will reject all numbers that conceal their number. Anyone calling from a number that blocks their number from appearing on your caller ID will not be able to reach you from that number. If someone calls you who is on your rejection list, they will get a message stating you are not accepting phone calls. This will make sure that their number is unable to call you. If you are receiving abusive phone calls from people you don’t know, it may be because they found your number somewhere. It’s important to share your number as little as possible to avoid abusive phone calls from strangers.  When making an online purchase, don’t include your phone number along with your personal information. It’s possible that your phone information could be leaked from the online purchaser and given to other parties. You can also keep your phone number out of telephone directories if you have a land-line. By calling your phone company, they should be able to keep your number out of forthcoming telephone directories. If the abusive phone calls don't stop, you may want to change your phone number. While this may be frustrating, it can be the best way to prevent abusive phone calls.   When you change your number, only give out your new number to close friends and family. If you don't know who is calling you, you want to be careful not to give your new number to the person calling you with abusive phone calls. Additionally, give out your number to as few businesses as possible. Since your number can always be leaked to third parties, you want to limit the places your number winds up. Your school should have technology policies regarding use. They may have some ideas on how to prevent abusive phone calls from happening at school.  When you're at school, only share your phone number with your immediate friends. Make sure they don't share it around to others. Your school should have a policies and procedures manual. See what it says about proper and safe technology use.

Summary:
Block phone numbers from abusive callers. Get call rejection from unknown numbers. Minimize the personal details you give out. Change your number if you feel particularly threatened. Ask your school about their technology policies.