Call ID blocking only works with other residential phones. You cannot block your phone number when you call a business, toll-free number or pay-per-minute number. The process is called ANI or Automatic Number Identification. ANI is approved by the FCC, automatically passed through to businesses by telephone companies and is not affected by call ID blocking.
There are no current regulations concerning the use of ANI and consequently, businesses which collect callers' telephone numbers are not required to inform callers that their phone number is being recorded. Since you called the business, you are now an existing business contact which gives the company the right to call you with their sales pitch, even though you have registered your telephone number on the Do Not Call List. The company may also sell your phone number to other companies.
Not all companies use your information for future sales calls or sell your information to other companies. For instance, my company 1-800-HURT-911, Inc. regards this information as private and has never sold information to other companies when people hurt in an accident call 1-800-HURT-911.
There are three ways that you can avoid having your telephone number used by companies for sales purposes.
1) When you call a business, toll-free number, or pay-per-minute number, tell the company that you do not want your information to be given out or sold to any other company. You can also tell them that you do not want the company to call you in the future if it is not related to your current question or concern.
2) Avoid calling any pay-per-minute number such as numbers in the 900 area code! Pay-per-minute numbers charge you a fee for calling them and are sure to collect, use and sell your phone number. Some examples of these types of numbers are lottery, horoscope, psychic, dating, and sex lines.
3) The best way to keep your number private and avoid unwanted calls is to use two telephone lines. Use one telephone line for calling businesses and for a fax if you have one. Use a second telephone line for friends and family.
I have one telephone line which I never answer. I use this telephone line to make outgoing calls to businesses and toll-free numbers. When companies ask me for my telephone number, I give them the number I called them from. If you have a home-based business, give this number as both your business and home number. I also use this telephone number on forms and on the Internet. Never give out your personal number to anyone but friends and family. When companies call me back, they can leave a message on my voicemail which is then e-mailed to me. If I'm expecting a callback which is important to me, then I will answer the phone. I never call companies or toll-free numbers from my second telephone number which I use for personal use. This number is only given to friends and family.
When using two telephone numbers, provided by your regular telephone company, it is important to have both numbers on one bill and to use the listed phone number for your business calls. The second phone number on your bill will not be listed. Never use a fax machine on your personal number. Many companies also collect fax numbers and you may get junk fax calls at all hours of the day and night.