Switch from Performance Internet to NOW Internet

Cancelled Performance Internet service/account; then subscribed to NOW Internet service, and promptly (next day) received the required Comcast Gateway/modem. Can NOW Internet be activated upon receipt, or do I (should I) wait until Last Day of Service on the Performance Internet account?

Cancellation happened in the Xfinity Store. Next day got email from xfinity@account saying 'Cancellation Request Received'. But the email's line 'Last Day of Service:' is not filled in. What's that mean?