Oh you want to upgrade your phone get the low use data plan
Then switch phones giving her the new phone
Then after a month of use go back to your old flip phone
Truthfully IDK if that works anymore, the reason to sell a smart phone at a upgrade discount is to get you on a data plan spending more money every month
I think you might find your line stuck with the data plan, or the phone deactivated when it goes on your wife's line
The place to look for info will be on HoFo aka Howardsforums.com
The are the number one phone info forums