Ignoring debt collectors won't stop them from calling you and harassing you. If they can't reach you, they will be calling your family and relatives, friends, ex lovers and spouses and ever your employers. The goal is to embarrass you enough to call them back.
There is only one way you can stop them - write a Cease & Desist letter to the deb collector. Once you send them such letter they are prohibited by law from further contact. If they violate your request, you can report them to the FTC and your state's Attorney General's office.
That's your right under the Fair Debt Collection Practices Act (FDCPA) and you can execute it at any time. Learn about it and apply it.
And trust me - it works! I have sent C & D letters to half a dozen debt collectors and I have not heard from them ever since.
Please note - even though C & D letter will stop debt collectors' calls it won't prevent them from suing you if that's what they want to do. You still owe them money and they can go after you in court.