Is it legal for a creditor to call and harrass you on your job?

Is it legal for a creditor to call and harrass you on your job? My boss has told them it's illegal. Is this true. They have been told on several occasions to stop.

According to the FDCPA (Fair Debt Collectors Practices Act), collectors must follow these rules: 1) A collector cannot call you after you’ve told them not to do so. 2) A collector cannot call you at work. 3) A collector cannot tell other people about your debt. 4) A collector cannot threaten you (with court, jail or other). And lastly, please don’t ever give a collector your bank account information or give them post-dated checks. You want a written agreement about how the debt will be paid before you pay a cent.

Letter example to send:
(Date)

To Whom it may concern:

I have been contacted by your company about a debt you allege I owe. I am instructing you not to contact me further in connection with this debt. Under the Fair Debt Collection Practices Act, a federal law, you may not contact me further once I have notified you not to do so.

Sincerely,

(Name)

(Account No.)