You have rights under the Federal Fair Debt and Collections Practices Act. These is a clearly described method for stopping creditor calls at home and/or work. Your state may also have collections practices rules that protect you. 8AM seems particularly early to be permitted.
In any case, your first step is to confirm who is calling you, and get a mailing address. Any effective communication that will have any legal power is going to have to be by mail. Read the Federal and State statutes that apply to you for more details.
My company has a custom 24 month program to resolve large debts, and we use these rules (and others) to stop the phone calls to our clients and put the ball back in your court. Our program isn't the perfect solution for everyone, but if we can help you I'll be glad to let you know. Call 888-221-2711 and ask for the Director. If I can't help you, I will help you find someone who can, and point you in the right direction.
Good luck, and remember collectors can't charge you extra for hanging up the phone.