Telemarketing calls
Federal law protects residential telephone customers from most unwanted telemarketing calls. Most violations occur when a business calls to advertise the sale of goods or services. There are two main types of calls: calls by live operators and those made by a recorded voice.

Most commercial advertising calls to a residence or cellular phone made by a recorded voice violate the law, and can result in a minimum of $500 damages paid to the resident. This amount can be increased by the court to up to $1,500 per violation if the caller acted willfully or knowingly. In many cases, residents can sue telemarketers for money damages.

Live telemarketing calls that advertise for-profit businesses are heavily regulated, and can also result in damages up to $500 to $1,500 per violation, when more than one illegal call has been made. First, telemarketers that advertise for-profit businesses are not allowed to call numbers that have been on the national do-not-call list for a certain period of time. You can add your home number to the list, or file a complaint with the Federal Trade Commission here: https://www.donotcall.gov

The Federal Communications Commission also accepts complaints about violations. Although it can’t hurt to complain to both, I suggest you complain to the FCC, because they are in charge of administering the Telephone Consumer Protection Act. You can file a complaint with the FCC here: http://svartifoss2.fcc.gov/cib/fcc475.cfm
Be wary of private organizations that try to charge a fee to reduce unwanted telemarketing calls.

Additional rules for telemarketing calls that are covered by the act:

• Recorded-voice messages must, at the beginning of the message, identify the person or business responsible for making the call
• Recorded-voice messages must provide a telephone number for the person or business responsible for making the call
• No telephone solicitations to residences are allowed after 9:00 pm or before 8:00 am.
• Those who make telemarketing calls to residences must maintain their own do-not-call list, must have a written policy available on demand, and must train their employees.
• Residents can demand that a telemarketer add their number to the caller’s own do-not-call list. The caller must honor this request within a reasonable time (not more than 30 days). This request must be honored for 5 years.

Some calls are exempt from portions of the TCPA. One exception is for callers who are tax-exempt non-profit organizations. However, some unscrupulous businesses hide behind non-profit organizations to conceal the true business purpose of their calls. Another exception is for calls that do not include or introduce an unsolicited advertisement or telephone solicitation (for example, political calls or legitimate surveys). Other exceptions include calls for emergency purposes, non-commercial calls, and calls to people who have an established business relationship with the caller. If you are receiving unwanted calls from a business you have dealt with in the past, you can end the business relationship by demanding to be added to the company’s do-not-call list.

Unsolicited Fax Advertisements
The Telephone Consumer Protection Act also prohibits unsolicited advertising to fax machines. Congress is currently considering changes to the rules for unsolicited fax advertising.

Violations of the fax rules can result in a minimum of $500 damages for the recipient. This amount can be increased by the court to up to $1,500 per violation if the sender acted willfully or knowingly. In many cases, residents can sue fax advertisers for money damages. Anyone receiving an illegal fax advertisement can recover damages – whether the ad was received at home or at a business.

Keep in mind that this is just general information about telemarketing and fax advertising. There is much more to the law governing telemarketing and fax ads. If you have a specific legal problem, or if you think you have a case against a telemarketer, contact an attorney to see if she or he can represent you.

There are other laws designed to protect people from particular wrongful business practices.
Here are a few:

Lemon Law
Telemarketing & Illegal Faxes
Truth in Lending Act
Unfair Debt Collection (FDCPA)