The FDCPA is the Fair Debt Collection Practices Act which protects comsumers from unlawful creditor actions. The most obvious way to stop creditors from calling you at home and work is to ask them to stop calling over the phone, but that may not work. If that does not work, then you should write a letter. You need to be clear about your desire to communicate through the mail only. You must also be clear that you do not want to receive any more phone calls, and you should cite the FDCPA.
When you write your letter to the creditor, the Federal Trade Commission (FTC) recommends that you should:
1) keep a copy of the letter you sent;
2) send the original letter by certified mail; and
3) get a return receipt.
Under the FDCPA, once a creditor receives your letter, they are not allowed to contact you again except to tell you they will not call you again or that they have decided to take action i.e. file a lawsuit.
If they continue to call after receiving your letter, then they may be in violation of the FDCPA. In this case, you should contact your state Attorney General's office, or the FTC and file a complaint.
Finally, you should seek legal help. The attorneys at 1st California Law Inc. can advise you of the appropriate course of action.