"Slamming" is the illegal practice of changing a person's communications provider without permission, and it can affect customer's local or long distance service.
Slamming prevention tips
AT&T recommends the following tips to help prevent slamming:
Take charge of incoming calls. Fraudulent callers may misrepresent themselves. If you doubt the identity of the caller, hang up. AT&T customers can contact an AT&T customer service representative for assistance.
Ask questions first. When a caller offers to switch your phone service to a new provider or requests sensitive information, ask questions. Verify the identity of the company, what it offers and at what price, and get contact information for the service representative. If you intend to switch only one service, such as long distance service, confirm that it is the only service to be affected.
Read telephone bills carefully. Make sure that you thoroughly understand the charges on your phone bill and that you only receive charges from the provider that you've chosen. If your local service has been changed, you will receive a final bill from the old provider and a notice of service disconnection.
Be suspicious of alleged changes to your service. Some AT&T customers have received calls or mailings from companies claiming to bill or provide services on behalf of AT&T. AT&T has not consolidated billing functions with an outside agency or communications provider.
How AT&T can help if you've been slammed:
Consumers should contest any charges imposed by the company that slammed them. According to the Federal Communications Commission (FCC), customers don't have to pay for services resulting from slamming for up to 30 days.