How do you prevent a collection agency from calling?

Just say, "No speak-a Ingles".

pay your bills on time!!!!!!!!

cancel your phone number or change them

Pay the bills is the best way. But when they were bothering me some time ago I started keeping track of who called and when. Write it down! After two weeks of this I told the next person who called that I was keeping track of how often I was being called and if they didn't quit I would file a harassment suit. The calls stopped.

Pay your bills.

If you are called at work, tell the caller that your employer does not allow personal calls at work and to please not to call your their. Usually, that will stop them from calling you at work.

As mentioned elsewhere, keep track of when you are called and ask them to stop. Otherwise, they are harassing you.

Finally, let's look at the problem... you are late on some bills and the collection agency wants the money. The agency has purchased the debt for 20%-30% of what you owe. So, they are trying to get the money. Negotiate with the agency. See if you can settle for 40%-60% of what you owe. Work out some arrangements.

Tell them to "cease and desist". They may request a letter.

They can only call when they transfer the debt to someone else.