deterrent: please pass this to your friends

When you get one of these calls, listen to the message and press the number requested to connect you to an operator. When they answer, tell them that you want to lower your credit card interest.
Tell them that you have over 5 thousand owed on your account so you qualify. When they ask you for your rate tell them you will have to look in up on you statement.
From this point on you can just let them hold until they hang up.
If you have extra time, just string them along with phony data.
The more time they are waiting; the fewer calls they can make. Maybe they will give up this method if everyone just wastes their time.