Consumer watchdogs say the problem of slamming has plagued the telecommunications industry since phone service became deregulated and competition grew to sign up customers. Slamming occurs when a customer -- without his or her consent -- is transferred from one long distance provider to another. Many consumers are not aware they've been slammed until they notice changes on their phone bill. Rob Tongren is the president of the National Association of State Utility Consumer Advocates. He says companies engaged in slamming have a number of ways to sign up unsuspecting customers.