Idearc took over the traditionally telco-owned YP a few years ago. The telcos now have nothing whatsoever to do with the YP/Superpages.
As I understand, the costs and the rules are much the same as when the telcos did YP. If you agree to a paid YP listing you are responsible for the year's cost whether you cancel or not.
When we cancelled our box ad at the end of the year (in July), Idearc continued to send us what looked like bills. In effect, they were pseudo-invoices, attempts to get us to reregister. They finally stopped sending them.
If you have any questions, call them to discuss it. Be prepared ~ they have very slick-talking sales people who will try their best to get you to buy in.