Actually, this is one you might want to call back - from the same number they called. The robot answer says to press 1 to be put on the do not call list.
When I called back it said 1 was asking to have someone call you, and 5 was to be taken off the call list. I just wanted to post that so other people make sure to listen to the message and choose the correct option.
PS: when I called from a different number, I was sent to voice mail with no option to be removed. I guess the system is smart enough to know that the number you are calling from is already on the call list.