If you were their customer they can call for up to 18 months even if you are on the DNC list. However, if you tell them not to call and they continue, you may be able to sue for harassment depending on the laws in your state. If indeed it is a business you previously used and a verbal request to stop calling is not honored, you can send a "cease and desist" letter by Certified Mail, Return Receipt demanding they stop calling you at your number. You would probably need the corporate headquarters address to send your demand letter to. If they fail to honor that request you can sue for I believe $1500 per call but you must keep records of dates and times of the calls and perhaps hit *57 to record their number with your phone company. You can then use the phone company records as proof in your lawsuit. You will probably need an attorney to proceed via the lawsuit route.