Updating my Norton LifeLock Select subscription

Are you saying you were not able to contact Support, or they were unable to resolve your issue?

If your old subscription has expired, try entering your new product key at My Norton - Login | Manage, Download or Setup an Account . Hopefully that will look after registering your new key and making any changes required to your 360 installation.
If that does not work, you will have to try Support again as noted by bjm_s comment about Amazon subscriptions.