If the tablet has the functionality for cellular data built in, the actual activation of said device is irrelevant....Once purchased it meets the 14 day criteria and does not qualify for the extended return period. It is also subject to a restocking fee as well, depending on your location.
I am a Best Buy Employee, but the views that I post are my own and not that of Best Buy.
***Know that I am not able to issue official responses and that my posts are only here to help before an official response is offered by a Best Buy Social Media Specialist***