1) Make sure you are on the Do Not Call list. They should scrub their call lists of your number within 30 days of adding your number to the DNC list.
2) You have already told them to stop calling, so they are required to put your number on their internal Do Not Call list.
Follow up with your request in writing, sent certified, return receipt requested, indicating the dates of their calls and that you told them on each call to stop calling. Send this letter to their legal department, or if you can't find that, to their executive offices.
Demand in your letter that they cease calling. At the bottom, add:
CC: FTC
CC: FCC
CC: <my state> AG
File a complaint with FTC, FCC, and your state AG for their existing DNC violations. Include in your complaint any caller id information, such as the telephone number. Telemarketers are required to send valid caller id information, to assist in enforcement of DNC and autodialer laws.
If they keep calling, contact a consumer protection attorney, or one that handles junk fax and telemarketing calls. Or file suit in small claims court. Look up TCPA.
http://www.fcc.gov/cgb/policy/telemarketing.htmlhttp://privatecitizen.com/tcpa.htmhttp://epic.org/privacy/telemarketing/http://www.discord.org/~lippard/lawsuits.html