It's such a problem that Missouri's attorney general has an entire Web page dedicated to it. Consumers say companies have "slammed" them by switching their long-distance phone carrier without their knowledge, or "crammed" their phone bill with unauthorized charges.

Doug Anderson doesn't know how long he paid $9.10 before he noticed. He also has no idea how it ended up on his bill in the first place.

“The last three to four months, I noticed the bill was $10 higher and never looked at until just the other day,” he said.

“It's constantly in the top five complaints year after year,” said Assistant Attorney General Ron Carrier.

Carrier says consumers usually get slammed or crammed when they enter contests and sweepstakes. Entry blanks may double as authorization forms to switch or add phone services.

You can also fall victim by signing "bonus checks" received in the mail, responding to offers of prizes and cash solicited by mail or responding to a caller offering a lower-priced phone plan or simply verifying your current plan.

“It's just frustrating that people can do this and get away with it and it's up to you to find them and prove you don't want it,” said Anderson. “The bad companies realize people don't go over their bills with fine toothed combs but you do need to do that? Make sure you're not paying for something you didn't sign up for.”

If you do find an unauthorized charge, Carrier says do what Anderson did.

“I said, ‘My next call is to the attorney general,’ and they said, ‘We'll credit you right now,’” Anderson said.

It's not always that easy. That’s why the attorney general has tips for how to avoid getting slammed and crammed and what to do if you are a victim.

That’s why the attorney general has tips for how to avoid getting slammed and crammed and what to do if you are a victim.