"If you'd rather have letters, then the next time they call, tell them you want them to stop calling you, and to contact you in writing instead. Then give them your address. If they don't comply with this, report them. (If you can, record your conversations with them.)"
That will do a person little good. Unfortunately, the vultures will fall to the floor laughing at that verbal request. If one wants the phone calls to stop, either fax or send via registered mail, a tactfully worded Cease and Desist letter. As an example, here's one that I've sucessfully used - though keep in mind it's geared for Ontario..
[Begin]
{Insert all relevant header formatting... Date line, address info, subject, reference #, etc..}
Pursuant to my rights under the Collection Agencies Act, R.S.O 1990, I am requesting that your office staff and any of its affiliates, cease and desist all attempts to communicate with any 3rd party (eg. my Family, Friends and/or Associates, etc.) with respect to [File #]; this is in addition to limiting any future communication with myself to regular postal mail.
Furthermore, your office has yet to supply me with documentation supporting proof of this alleged debt; therefore, I dispute the debt in question and feel that it would be beneficial to all parties if your client would initiate legal proceedings. Should your client wish to discuss the matter with me before filing a suit, have a member of THEIR office contact me directly.
{Print Name - Do not sign; this is not required}
[End]
Notice how I used the wording "Alleged debt" ... It's VERY important to refrain from acknowledging the debt in writting. Good Luck!