Hey 562deb562. Since you mention that you've been calling numbers like these for some time, I'd guess that the Out-Of-Plan-Numbers message may have caught you by surprise - I'm sorry about that. Our unlimited talk and text plans are intended for direct communication between two people (or three-way calling completed through your native dialer) - so in that sense, calls connecting to this limited group of numbers have always been "out of plan". Connecting these out-of-plan calls has always cost more than connecting other calls, but the practice to help recover some of the cost with a small usage fee is new, you are 100% right about that - if we advised you otherwise, I apologize.
Potential charges for specific numbers is referenced in the T-Mobile Terms and Conditions under the section headed *How Will I Be Billed For Use Of The Services - though they're not addressed by name. In older versions of the T&C, I believe the potential for charges was alluded to in the Billing Information > Usage section, but loosely. I think that the document that gramps28 linked to does a better job of explaining these specific fees than our T&C.
If at any point you encounter the Out-Of-Plan message on a call that you don't think should be part of this subset of numbers - say, to a person's mobile number, home or business, and not a chat, conference, or broadcast line (for example), then we would definitely love to hear from you so that we can investigate and correct the matter.
Thank you very much for your feedback on this and for taking the time to post here, and again please accept my apology if we handled this in a way that seemed less than transparent - we always want to be open with our customers.