This number seems not to have been used very frequently over the past several years.
The main number that Neilson TV Rating has used around here is this:

http://800notes.com/Phone.aspx/1-813-366-9800

They try calling from this number if they get no answer using that other number. They've been calling no more than once a day from each number. It's just a matter of family policy that we don't answer unknown calls or questions from strangers on a phone.  Of course any kind of survey is potentially just a phishing trip for usable personal information.