I got a call several times this week, offering to lower the interest rate on my credit cards (I have no credit cards).  The prerecorded message said press one to speak to someone but two to be removed.  2 doesn't work, so I pressed one and the woman who answered (eventually) had no idea what number I was calling from.  I told her I was on the do not call list and asked her to remove me.  She asked what number I was calling from, so I replied "you called me and you don't know what number?  I am on the do not call list, do I have to make a complaint?" She hung up on me.
I used caller ID and did a search and found this site after I registred my complaint on the Do Not Call list site.