You open your credit card bill and discover a charge that isn't yours.

The solution might be as simple as a quick phone call or a short letter. However, the credit card dispute could involve a series of calls and correspondence and a little more time, depending on the situation.

Mistakes happen, says Howard Dvorkin, author of "Credit Hell: How to Dig Out of Debt," and founder of Consolidated Credit Counseling Services Inc.

"People just need to understand the law and how it affects them," he says. "And don't be afraid to dispute something."

The first question you want to answer: Was this a billing error or a case of credit card fraud or theft? While you may not care how the extra charges found their way onto your bill, it could make a difference in how you handle the dispute.

Short of consulting attorneys, going to court or complaining to regulators, here are the seven steps you need to take if you find an unfamiliar charge on your credit card bill.