[Sleeep]

That says nothing about phone numbers, just addresses.

Selling an address updating service to parties that already have your address is not the same as "straight up sell[ing] your phone number when you move."

From the horses mouth:

"The information you supply will be used to provide you with the requested mail forwarding and related services. Please be aware that this service is voluntary, and that requested information is required to provide the service. Collection of information for this service is authorized by 39 U.S.C. §403 and 404. We do not disclose your personal information to anyone, except in accordance with the Privacy Act. Authorized disclosures include limited circumstances such as the following ... to mailers, if already in possession of your name and old mailing address, as an address correction service. Information will also be provided to licensed service providers of the USPS to perform mailing list correction service of lists containing your name and old address. A list of these licensed service providers can be obtained at the following URL: http://ribbs.usps.gov/ncoalink /documents/tech_guides/CERTIFIED_LICENSEES"

They imply they only provide the new address but saying "the information you supply" leaves it open to for them to provide your phone number along with your new address.