Did you say 12 thousand minutes? Maybe (cringe) you should get a lawyer.
How about this? Explain it to a sympathetic neighbor & ask their help in catching the phone company misstating the facts again. A neighbor who doesn't have the CPP.
Find out about whate your state law is about recording phone calls & comply with it. Some companies on their announcement will say "calls may be monitored to ensure quality service" does that mean not only are you allowing them this intrusion, but that they are at the same time giving up their own privacy? I don't know.
Once you know you can comply with the law,
go to your neighbor's & have them attach to the phone terminal a device to plug in to a cassette recorder (both should be available at Radio Shack) that will enable recording.
Then have the neighbor phone up THE COMPANY and go through exactly the same thing (ask about the CPP, etc.} that you went through, asking the same question about the same telephone number, and get the answer on tape. If they give the information wrong again, you have a nice piece of evidence to confront the billing department with (save the original of the tape).
If you don't want to risk putting out money for this first, you could just have the neighbor call and ask the question & see what they tell the neighbor. You might be listening on an extension, introduced as a friend who understands these things better than the neighbor who seems as if he's a bit slow.
The neighbor doesn't necessarily have to actually go through with the order.
Another alternative is a protest to the regulatory agency in your state, or in some cases the FCC. It depends on how these "long distance" calls are carried.
[size=4][red]P.R.K.