Debt collectors? No problem! Call blocking is the way to go! Never get a call from a number you don't recognize only a voice mail message that you can listen to if you so please.
ARS National Services out of California, when you call them back, they will have your number in their system (since my phone is a cell phone, they were after a former owner of my #).
Man called asking for my husband, said he was not home, asked if there was message, man said no he would call back. Husband came home and called number back, woman answered, and knew my husband's name, and told him to hold a minute, original man came on line and asked my husband for his bank account number? My husband hung up.
This caller was told he/she had the wrong number the first two times but called a third time. Obviously not bright. I did not know the person being called.